Hi Seenowayout,
A big thing I had to learn with my upwBPD is how to approach those same exact circumstances you mentioned. Before I elaborate on that... .have you read through any of the articles and lessons available for us partners here trying to understand our SO's? If not, I think you'd really find a lot of them enlightening and helpful in not only this situation but many others.
Elaborating on what I started to say... .Criticism is one of those things that PD or not most people have a hard time swallowing. Even constructive criticism sometimes tends to hit a nerve we weren't expecting it to hit. What I've learned by going through similar things such as you mentioned as well as from diving into learning more about BPD as a whole, sometimes, a lot of times, criticism is received by our SO's as negative in a "I'm bad" -- "I'm not good enough" -- "I cant do anything right!" kind of way. This brings out a lot of emotions that, from my experiences, turn into anger and 'retreat'. Like I've often read on here and other places: Emotions/Feelings = Reality to our BPDs
Speaking on personal experiences: Before I took the time to stop and think about how I was going to position my "criticism" of things my GF was doing, I would blurt it out in a very straight forward way that I assumed she would take as constructive criticism we would come to a compromise on. The problem was (and still sometimes is) that for her it would lead to feeling like she wasnt enough. That she'd done something to make me see her in a negative/bad light and she just cant handle that being the perfectionist that she is. I noticed this would lead to her overthinking so much that eventually it would somehow get her into a place where she was now convinced I would leave her because I didnt like when she did XYZ.
Cycle:- I try to offer constructive criticism assuming we could find a solution where everyone would be happy
- She sees it as be criticizing her very being which leads to an overload of thoughts/feelings/emotions
- She starts expressing these thoughts/feelings/emotions which are for the most part misaligned with the situation and I JADE
- Full blown episode
... .and now we're both really unhappy.
I'm pretty new to these boards so please look for other advise from the vets on here but, I think the examples you provided look like a very excellent time for you to work in
SET. You can find lessons on SET on this website. I'd give them a read. I will tell ya this though... .I just started really trying to implement it. Takes a lot of practice and I'm still not always sure I'm doing it right. Baby steps!

Any thoughts from others?