Don't bother with ultimatums or counselling, he won't change, because he thinks he's in the right, so it's just a waste of time. You have tried, but it's not you that needs to do anything, it's him, and he's not willing.
Leave now, while your child is still a toddler, so it won't upset them so much.
Getting your ducks in a row, just means getting legal advice, getting copies of all the finances etc, look to see if there are any benefits you can claim if you're on a low income, start saving money so that you can afford to move out, etc. Basically, getting ready to leave.
Also, if close family and friends don't know what's going on in your relationship, tell them, but don't listen to advice that says you should keep trying with him. Some people believe that you shouldn't divorce, and that's "just how men are". Try to get emotional support from them.
Only go to counselling on your own, if you feel you need to.
BTW, it's helpful to mention the country you're in, in your first post, otherwise people will be giving you advice that's UK specific, like the mention of Tax Credits, which is a benefit available here.