I'm somewhat bemused by the fact that you've had possession of the key to the kingdom downstairs toilet/storage room since you've been posting here but didn't think to retrieve your passports/birth certs/other documents. What type of lock is on the door?
How did you come to acquire a passport for your ds without his birth certificate being returned folded "creased"? In any event, this site tells you how to claim child benefit and how to buy another birth certificate if necessary and there'll be no need for him to know that you've claimed for ds. www.gov.uk/child-benefit/how-to-claim
Given that, following your breakdown, you were staying with your dps while the dc remained with him in London, you were properly informed to return and leave properly by which I take it that you were advised to apply to Women's Aid for a refuge placement for you and the dc where, as I've said upthread, you will receive all the help you need to apply for benefits, social housing and, most importantly, defend any legal proceedings he may institute with regard to a childcare arrangements order*.
For obvious reasons Women's Aid won't be place you and the dc in a refuge near your current home, but there's no reason why you can't ask to be placed near your dps and, indeed, to make application for social housing within a short distance of their home. In common with numerous other resources/services in the capital, WA are overburdened by demand and overstretched staffwise and I see no reason to suppose that you have cause for complaint because you were informed that there is a 12 month waiting list for counselling but that they were on hand to help if you needed a refuge placement.
How long were you in hospital and did you stay on a pysch ward or were you admitted to a mental hospital/unit? Was the 'trauma to the dc' caused by them witnessing you putting your hand through a window, or were they receiving counselling before this incident? Who cared for the dc during the time you were away?
Fwiw, albeit that it is a form of control, I don't see withholding a key to the front door as akin to being held prisoner as you went out and about with him but, presumably, did not want to go out on your own in case he wasn't at home when you returned.
*formerly residence orders.