The note laying out all of the expenses that your h has incurred while driving the car will most likely fall on deaf ears. However, I do understand why you put everything in writing. However, the only thing you needed to stand firm on was him not driving it because he has a suspended license. You do not want him out there driving around and possibly having an accident w/his license issue and, of course, your insurance company may look at what he did and question whether you knew he was driving on not. Plain and simple, "h, no you cannot drive the car until your license has been reinstated". That is what you say next time. The court and his over bearing lawyer should agree w/that statement.
I may be wrong, but the wife of your kids' godfather isn't going to be too happy that you are contacting her. Whatever it is her husband is doing is between him and your h. She may not want to be involved or get involved in the situation. I know you felt that this was something you needed to do, but it may back fire on you and make things a tad more difficult when dealing w/your h. I know, how can it be any worse...but your h has a way of twisting things and making you look a it batty to others. Bottom line, people to do not want get involved in such messy situations and she may very well either ignore your letter or post to you to not contact her again. Either way, your h will take that missive to his lawyer and he'll be growling again about your behavior. So, be prepared for that.
I think it is a wonderful idea for your son to work a little bit. It will give him something else to think about and help his self esteem greatly.
Let me just say this, Gerda, you are not a bad person.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.