You are clearly bright. I think you should maintain the status quo and keep your head down at home. Don’t let on you are not happy.
Start a secret folder in your phone and password protect it. I don’t think this man has your best interests at heart and from now you have to look after yourself.
Read Fair Play by Eve Rodesky and follow The Abby Eckle on SM. Start educating yourself about your position here. Research financial abuse. Research coercive control. See if it fits.
Look up pathways back into work - is there a way to do a top up and get back into pharmacy? If not how else can you use that learning? You have skills that are transferable. Research Assustant for example.
Go to Citizens advice and get some info on what you’d be entitled to. The fact that he is the children’s father is really his only responsibility to you (legally) I think, but they will have advice. Get benefits advice and housing advice. Also they will know of any grants or hardship funds to help with study.
It sounds like you have no access to money - how do you pay for your needs like clothes etc? How you pay for food? Try to start squirrelling cash away and hide it so you have some, then open your own bank account with it. If you get birthday money or Xmas money from relatives then save it. Sell stuff on vinted. Start secretly getting as much as you can saved.
Get as much information as you can about his business and assets etc. Bank accounts etc. get his NI number if you can - needed for a child maintenance claim.
When you have as much information as you can get, have a conversation with him. Let him know that you have realised that you are in a very vulnerable situation financially and that you either need him to fund childcare so that you can study/work, or start paying for your services. His response, if he loves you, will be to support you to feel more secure. If he won’t then that useful information for you.
If he won’t then you go on strike. Don’t leave the house unless you/the kids are unsafe. Anything you do outside of the same hours that he works should be paid for (or he needs to do half at those times). He is benefitting from your labour. Without you he’d have to clean, cook, etc for himself. If he won’t then go on strike - don’t wash his clothes, don’t cook for him. Just do what the kids need no more. Stop keeping the house to a high standard. Buy food that you and the kids like etc. With the time you save, study.
You might have to stay (if you are safe) until they are both in school.