Hello Somerset
Welcome to bpdfamily. I'm sorry you're struggling with your mother and husband.
I understand that it's important to stay in the here and now and not rehash past grievances or even out right disasters. However, I feel like I'm being asked to just let people do what they want and relieve them of the responsibility of apologizing or accepting that they were confusing or hurtful. Sometimes it's minor and I wonder if I'm the one being too sensitive.
First of all Somerset the only way to get past our pasts and on the road to recovery is to have the courage to reach out, open up and talk about what's happened or what's going on. It's difficult to find clarity with our memories and emotions playing tug of war bottled up in our own minds. Kuddos to you for having the courage to reach out to start the process of recovery.

For example, my husband (who most certainly does not have BPD) and I were discussing finances. I was trying to ask questions about long term planning and he was flippant with answers, giving me vague answers, joking about not needing money when we're old because we'll be preparing to die, etc. I found it annoying and let him know that I found it annoying, could he please give more serious answers.
It sounds reasonable for you to want to be serious in talks about your future with your husband. You two are partners. Both adults, responsible for your financial future together. Does this happen every time there is a conversation about finances? If so, I would find this annoying too.
I want to share some communication techniques that will help with these conversations with your husband and your mother. Specifically DEARMAN. This techniques, along with the others mentioned, have worked well with my mother and I've used them with friends/coworkers. The skills take some practice but over time they can pay off.
Communication tools (SET, PUVAS, DEARMAN) <---- click here
I'm all for moving on and starting over, but apologies mean a lot to me and I get worn down by just taking things and not hearing other people recognize that they also could have done a better job. I also don't see how things can be easier in the future if patterns are not recognized and a plan made to alter them.
Have you ever discussed how much apologies mean to you? Have you ever asked for one? If not, that's a pattern too. It's hard to make a plan to change patterns when they aren't recognized and I've found not many look for patterns in themselves. Accountability is difficult topic for some. Those of us that were raised by parents who put all of the responsibility on our shoulders find it difficult to stand up for what's ours and what belongs to someone else in the responsibility department.
These types of interactions also worry me because my mother has uBPD and we have been struggling with each other lately. When I hear my husband say things like "You're over reacting", "You're reacting to me", "You aren't making sense", "I'm confused", "I can't say anything to you right now because you'll just react", I wonder if I am behaving in ways similar to my mother's.
Sounds like a pattern and good for you for recognizing it. These statements are invalidating. My mother uses them too, it's been her way in the past to control me when things get uncomfortable for her. I recognize them for what they are today, red flags to me that mom is feeling uncomfortable and I move right into the communication skills I've shared above. These statements are your cue that someone ELSE is "rattled" and is looking for a way out of their discomfort. You are not responsible for the way someone else controls their feelings, you are responsible for being clear in your communication style. For being clear in what you need in a calm manner. When statements such as these get us rattled it's hard to think clearly, much less to remain calm if we aren't used to being free to express our needs. This takes some practice too.
I feel diminished when he says things like that and it does silence me or trigger me into pushing harder to get him to respond. But again, the worry that maybe I AM unreasonable and am somehow communicating very ineffectively nags at my mind and I respond by saying less and trying to stay out of people's way. I have a hard time judging my own responses as valid or not if they conflict with the other person in a conversation.
This takes balancing our gut feelings Somerset. A lifetime of cognitive dissonance will cause us to question our gut feelings. If we are told over and over something that our gut feelings disagree with it causes anxiety and people pleasing or giving in when we doubt our gut feelings alleviates or lessons the anxiety. This is how WE deal with the discomfort. Turning this around is a practice in becoming comfortable with the uncomfortable. This is learned behavior and it can be unlearned.
A couple of weeks later she did let me know that she had checked paper calendars from 7 years prior to confirm that I was indeed at an appt. with her. At least she did that and let me know.
This is a big deal. Did you reward her, thank her, for this acknowledgement? Reward positive behavior.
she went from refusing contact/visits from me and my family for 3 months, wanting it to resume as before as soon as we had one unproductive and unpleasant joint counseling session to now agreeing to not have joint counselling and wanting us to just be kind to each other.
Will this work for you? Is joint counselling working out? Have you considered individual therapy with what you've been up against? My therapist has been a Godsend. Therapy is also one of the highest forms of self care.
She said she just doesn't understand why I react so badly to things she says that any other person would just laugh at or shrug their shoulders, that she doesn't treat me any different than she does anyone else.
More invalidating statements. These are your flags that the conversation is making HER uncomfortable and she is looking for an out. This is also where WE learn to identify our values and determine our boundaries.
BOUNDARIES: Upholding our values and independence <--- click here
I'm hurt and angry. I'm very worried that I will say the wrong thing or try to defend myself, thereby landing me in hot water again.
Your feelings are valid Somerset. What does hot water look like? Meaning, what happens outside of your mother going no contact for a bit? I had to reach a point of not feeling guilty and taking full responsibility if my mother got angry or sad. It takes two to tango, I own my part, not hers. If your mother needs some time to get her emotions under control to be in contact is that ok? What about you, do you ever need some space as well and do you take that space/time for yourself?
Maybe I really am the problem and not her. I go back and forth about this.
Going back and forth on who is to blame is to be expected however do remember it takes two to tango. We can't accept full responsibility for both involved, only ourselves.
I have 5 children and I seem to be doing a very good job with them--they are happy, polite, largely well behaved, we get along well enough to home school them where they are all thriving and have many friends, I have minimal conflicts with my husband (barring these frustrating exchanges from time to time) and I have many long term, in constant contact friends with little to no conflict.
Sounds like a healthy, loving family.
at almost 40 years old, I've been pulled aside as I'm walking past a room, pulled aside to be hissed at in my ear about being rude to her, my children are watching and they'll learn to be rude to me. Those interactions leave me feeling shaky inside.
I'm sorry you've gone through all of this with your mother. This would leave me shaky inside too. It would be upsetting.
I do know that I make things worse and I am humiliated by the fact that I can't just waltz into an interaction with my mother and be guaranteed a relaxed experience.
You've come to the right place to learn how to NOT make things worse. I'm looking forward to hearing more of your story.
Welcome to our family Somerset.