You are not a horrible person. Let's get that straight right now.
FWIW, if you can't drive, it does seem odd for you to have to chip in with insurance, especially if you don't use the car much at all, and if money is tight then your playgroup would naturally take more importance.
I know you are angry, and frustrated, and perhaps this is actually working against you.
Hmm, men don't do the I messed up and made a mistake thing too well very often, IME.
I think you need to change your tactics. There are issues that are important and do need to be discussed calmly.
Can you take a little time for yourself, to calmly jot down the money you have, the things you have to pay, both you and him and ask him to help you sort out what needs paying and what could do with being reduced.
You mention that you had depression and have had issues with PMT etc. you say they are treated, but from here you sound so angry, raging. If you find that you are ranting most of the time, then perhaps you might benefit from a chat with the Dr to see if he can't give you something to calm you down short term, so that you can find a quieter place to gather your thoughts and think clearly enough to know what to do.
It's true, if money is tight, then WTH is he doing with a stash that is HIS? If he is hoarding money, yet asking you to chip in for things you don't even use, when the money you have is counted and spoken for, and is tight, then tbh, he's being unreasonable, and needs calling out on it. But screaming rarely works, you just show them that you have lost control, and that weakens your position. (speaking from experience here.. )
Do what you can to calm yourself, it will do harm to everyone, and won't help anyone solve anything.
then look at the issues you have calmly and bit by bit. one thing at a time, so it's not overwhelming and you both manage to keep focussed on the issue, and not get swamped in the bigger picture.