Hi, I’m Dr. Jackie, an interpersonal communication researcher/professor and relationship expert. I want to help you. And I'm so sorry you are going through this turmoil.
I hesitate to say that you are too sensitive or even comment on how either of you are handling the argument because I am only seeing a written account. However, from what you have shared here (and thank you for so many specific details that really help provide the big picture), it seems like you are right in that he sees a lot of these things you fight about as little and insignificant. But even if he is right in that it seems like he thinks you over-react, the fact remains that you have been hurt and have shared this with him. So regardless if he thinks these things are too insignificant to fight over, he should try to be more understanding of your feelings.
Also, another big concern I have is that it appears as though he is holding his financial help over your head as a way to have power or control. Maybe this is not the case, but from reading "between the lines here," that is what I sense. And here is the problem: whenever one person feels indebted or like s/he owes the other person, this imbalance in "power" can really cause disruption in the relational communication. You point this out in the end with, "He says he wants to work it out and work on our communication..." This definitely is a two-way street in that both of you need to listen to the other person. Like you said too, if this is occurring in just about every argument, and you argue often after 4 years, statistically, there is only about a 1% chance of this just suddenly changing. The vast majority of the time, things only become more filled with conflict as the downward spiral of the relationship continues. About the only thing that could change this is some type of "intervention," such as a near-death experience, tragedy, or counseling/therapy. Just like a person addicted to alcohol or drugs rarely quits on his/her own, people typically do not resolve their conflicts on their own. But a counselor (and face-to-face is always my first suggestion) can help you two work on this. If he is serious about working things out, then he should agree to counseling. But even if he does not go, please please consider counseling for yourself so that you can work through this with a therapist and really explore if you think this relationship can work.
I'm going to send you my contact information (phone and Skype) if you want to use either one of these formats to chat with me. Or of course, you can reply here as well.
Please let me know if this helps and what I can do. Take good care,