Hey GreenOlive, glad you reached out for some support -- and

What a hard place you're in right now. It just reads like things have been slipping through your fingers the last few years, and you've had to watch but haven't felt like you could stop the trainwreck. Really difficult and painful... to say nothing of confusing, like you mentioned.
You shared that you feel like you don't even recognize her... were things different before you got married? Was there "an event" that happened where you can say "yeah, that's when things started to get bad", or not really?
Do the two of you have any kids together?
Did/does your W work outside the home?
And you mentioned that she does have a depression diagnosis... is she still seeing the provider who diagnosed her, and is she on any meds?
What about you -- have you started any therapy or counseling for yourself?
...
There have definitely been members here who've coped with having spouses similar to yours -- maybe the issues aren't as overt (yelling, violence, hitting), but just the sense that basic life is totally overwhelming for her. Members in those situations have also struggled with feeling resentful, too, wanting their spouses to function again. It's not easy.
Some people do suggest framing BPD as an "emotional disability", and that the two of you are in an "emotional special needs" relationship. An analogy could be: just like a person using a wheelchair would not be able to do her fair share of getting things off the top shelf, your W will also not be able to do her fair share of relational tasks. BPD can be pretty severely relationally impairing (as you are experiencing), and it makes a lot of sense that you'd be feeling angry as she does less and less and you do more and more.
While there are no guarantees, it's certainly possible that things can turn around in your relationship. It'll be less about "say these magic words" and probably a lot more about the choices you make that are 100% under your control.
Choosing to get some support here is a great choice

Choosing to get therapy/counseling for yourself (whether she joins or not) is another really good idea.
It may be that part of your journey is grieving the real loss of the marriage you wished for, and coming to terms with the marriage as it is in the moment. A counselor/therapist could be a good resources for that process.
As odd as it sounds, some members, after
radically accepting the significant limitations that BPD (and any mental health challenge) brings to the relationship, can find a way that it's "good enough" -- can find moments and times and aspects that make the relationship worth it, even with major "special needs".
None of this is easy... we'll be here for you on your journey.
kells76