Oh sweetheart - people absolutely would believe it and it is something many people fall victim to.
Whether it was intentional abuse on his part or whether he has is own mental health issues which cause him to be the way he is with money, the way he has treated you, intentionally or not is abusive.
With the hoarding on top of that, it isn't surprising that your mental health has taken a hit.
I know you have said you love him, but you really really need to think of yourself right now. Separation and divorce is hard enough in any circumstances, but with everything you have going on it is compounded and is 100 times more difficult.
I get you want to help him, but you won't be able to do that if you are too unwell or even worse not here anymore.
There will be time to think of him when you are sorted (if you still want to by then). If you want to help him sort his own life out, you will be able to do that with moral support, knowing that your own finances are sorted and you have a clean and tidy home to go back to.
For now, concentrate on the life you will have with your own place and space, knowing that your money is working hard in the correct savings accounts, investments and pensions.
Work on those business ideas, decide what art work you are going to buy to fill your new home and how you are going to put those interior design skills to good use. Get that solicitor in place and move towards that future!