I say this with heartfelt sympathy OP, as someone who has been there and also got out of the situation.
Your own mental health will be exacerbated by your husbands mental health problems. I know he is unwell and it's not his fault but if he is not willing to do anything to help himself, there's not much you can do. A person with mental health problems cannot effectively look after another person with mental health issues. It's a recipe for disaster. Unless your husband accepts treatment (as in medication etc) then nothing is going to change. It's that old saying of you can't keep doing the same thing and expect different results.
If it was me, my first step would be to explain kindly to your husband what affect his OCD is having on the children. Explain that he needs to take medication for his own sake and for his children's sake. I would even go as far as telling him he was being selfish for not doing so.
If he refuses to help himself and the family, I would seriously consider your living arrangements going forward. At the heart of the matter, you need to think: what is the best situation for the children? Not you or your husband, but the children.
Stripping a child down to look for bruises every time he has been out is emotional abuse. I have been told this by a social worker in regards to a case with similar behaviour. Teaching a child to be paranoid that everyone is a threat and could potentially cause bruises to them is emotional/psychological abuse. Having to bow to their dads very unreasonable demands which are completely out of the ordinary, making the children walk on eggshells constantly, is emotional abuse.
I say this as kindly as possible because I do know how hard it is to be proactive and change things. It's scary and you do panic about being able to cope. I also know that your own mental health would be so much better without your husband around. It would encourage you to make your own decisions, learn to look after your children as well as be able to live the life you want, and not be dictated to by another adult.
Always have in the forefront of your mind that it's about the children - what do they need? And no, keeping the family together is not always the best option. If I had done that, my children would have had a horrendous childhood and upbringing and would have had serious mental health issues. Now they are older, they thanked me for not staying as they have seen themselves how their father is.
Please take a step back and look at this situation from an outsiders perspective and don't focus on what your husband needs, but rather what your children need.