I look at this as him trying to communicate to you that he doesn't want to do something. His ability to communicate is so limited right now, it's great that he's learning how to do it in whatever way he can.

We had major issues with the car seat, too, and the only things that really worked well were patience and distraction, which it sounds like you're doing.

If my daughter expresses to me in any way that she doesn't want to sit down for dinner, I respect that and let her stay down playing if she wants. I let her know that I'm sitting down because I want to eat, and to let me know if she decides to sit down and eat.

It is hard when our desires conflict with our daughter's. We try to minimize our expectations that she is going to want to do what we want her to do all of the time. When we do encounter a situation where we really want something she doesn't, we try to explain our feelings about it and brainstorm ideas out loud about how we can meet all of our needs. (ie, you don't want to get in your car seat, do you? I really want you to get in because I don't want to be late to ... Can we make it more fun for you by bringing your special book? etc.)

Hope you are able to find peace with this!