The silent treatment and the threats are abusive. I’ve worked in domestic abuse for years, I have no doubt he was aware of your vulnerability and has used that as a way to control you.
I totally understand the need to get away as soon as possible, the best way to do that in your situation is to have a plan.
You will need your mental health team on board so talking to them is a good move. They will be concerned about you being alone in a strange flat, have a good think about the supports you have around you and have a plan you can talk to them about. For example, if your mental health takes a dip how will you know (what are the signs you recognise) and what will you do (eg using mental health team support, having someone stay with you, check in on you, presenting at hospital. What will you do if you feel suicidal? They have a safeguarding responsibility for you so they need to know you’re safe, and won’t necessarily agree that you’ll be much better away from him, especially if he’s been viewed as a protective factor until now.
Also plan to leave, look at where the money will come from for your flat. You don’t need his permission or agreement to leave, or to withdraw your money from the family “pot”, but you will need to be quite strong to follow that through given he is controlling - his controlling behaviour will likely ramp up as you try to leave.
Start getting together the things you need eg paperwork (birth certificates, mortgage statement if you have one, payslips, financial information) and keep them somewhere safe. Look at things that are precious to you, if you can start moving them to a friends house bit by bit. Assume you won’t get furniture etc so look at Facebook market place etc folk give all kinds of things away for free.
Can you afford the flat you’ve seen on your own salary? If not is there another option.
One option is to seek refuge at Womens Aid. That would mean you had day by day support (which might alleviate the concerns of the mental health team) and they can help you sort the practicalities of moving on. Please don’t think you don’t “deserve” their support, as a vulnerable adult in an abusive relationship your exactly the kind of person they’re set up to help.
I wish you the very best of luck, you’re so brave and have shown so much resilience- just a bit more and you’ll be free.