Yes, these relationships do have a spongey quality to it. While the going is good this can be comforting, but when things aren't going well or the people are separated, I think the sponge can be quite draining. This is especially true when the two are seeing each other for reasons other than their relationship.
I think if you're describing yourself as leaving in tears, what might help here is a clear consciousness of his issues and his emotions. When we aren't aware of how these things are moving from the pwBPD to us, it can cause us to be affected in unhealthy ways.
First, I'd suggest to stay mindful during your interactions with him. Remember to validate
yourself while you're with him. This will help you to keep a healthy state of mind.
Second, you may want to be more aware of keeping your feelings separate from the other person. It's quite well accepted that pwBPDs project feelings, and if this is the case for your experience (as it seems), this strategy an help you prevent projection.
I'm glad to hear that you care a lot about your job. I think that's very helpful.
I hope these ideas will be helpful to you while you resolve the little issues. For the practical issues you described, I know it might seem silly, but you might consider increasing the number of hours you work so that you can resolve the other issues faster. I think this form of self-care.
Validation:
https://bpdfamily.com/content/communication-skills-dont-be-invalidatingOne way to look at emotional separation using a work relationship:
https://bpdfamily.com/message_board/index.php?topic=292279.msg12749089#msg12749089A good way to look at emotional separation:
Strength: You will need the strength to be able to emotionally detach at times from your SO, to be able to separate his/her issues from your own, and to not take personally the behavior of your SO. You need a very strong sense of identity and worth in yourself.
