@mouseymouse123
As far as 'ducks in a row', here are my suggestions.
Make an appointment with a solicitor. This isn't to 'file anything', it's to educate yourself as to what divorce may mean to you.
Make a list of questions to ask the solicitor. If you can take someone reliable with you as a second set of ears, a 'question prompter', and/or a note taker do so.
Before the solicitor appt:
Gather all financial documents you can get your hands on or make a list. Mortgage and deeds (names on them and mortgage amount/balance), both of your incomes and pensions (if not his amounts, do you know the 'sources'), asset information (again, if you don't know his amounts do you know where accounts are), household 'outgoings'. If there are drawers or cabinets you can go through to get this info, do it! Heck, search the wastepaper bins. You'll want these to have a 'snapshot' of finances to show the solicitor. This can help with giving you an idea of what type of settlement you may expect and what child maintenance might be.
Think about the house and what you might want. Buy him out? Him buy you out? Sell and split the profit?
Think about what you'd like for child access. 50/50? EOW? The solicitor can tell you what is realistic.
I know doing the above sounds daunting, but once you get starting you'll get your momentum and finish the tasks. And you don't have to make any final decisions now. The solicitor is a 'fact finding mission'. If you don't manage to gather all, go anyway.
Next, if you can, gather together passports and birth certs for yourself and the DC. Your marriage certificate too. And get them to your mum's for safekeeping. Same for any financial documents you locate (hard in these days of online I know!).
After that, are there precious objects, photos, sentimental items that you don't want to lose? To Mum's with them, too. You've already told him you want a divorce, so these things going 'walkies' don't really need to be snuck out.
Right now, no matter what you've already told him, go stealth. Do NOT tell him you're seeing a solicitor. Do NOT tell him any plans and do not mention divorce again if he doesn't. If he does, do NOT discuss divorce with him or agree to anything. Remember "I don't know" and "I'll have to think about that". Those should be your answers to any questions he has.
I'm sorry this has happened to you. I know you feel as if every ounce of strength has been zapped out of you. But it hasn't. It's still there. All it takes for you to find it again is to take one step towards securing your own and your DC's future. Knowledge is power. Forewarned is forearmed.
Remember that 1000s of women have been where you are and 1000s will follow you. You are not alone.