hey. i'm not sure i have any advice but wanted to reply because i relate. i have bpd and what i really struggle with is low mood that lasts for quite a long time during which time i cut myself off from everyone because of havign no energy and basically fail to function, which is horrible.
i think what helps me is knowign that it will pass. even if it takes months, or a year, it will pass. however low i feel, it is not a forever thing. and knowing that means i can sit through it and not engage in destructive behaviour.
you say your team can't help much - i also don't find simply talking to people helps because it doesn't change anything. but i have found it helpful to work with people to come up with a plan of things to do when i am very low. have they been able to suggest anything you could do to help yourself? is the od risk the only reason they don't think meds are a good idea? because if they believe they may help, what about weekly or even daily prescriptions? i used to always pick mine up weekly.
it's great that you are trying with mindfulness and self care. i totally understand that it is frustrating when it takes a while to help. but i guess what i would say, is hold onto the fact that they do help, even if it isn't as much as you would like, and keep doing it. because the more you do it the easier it will be and the more it will help.
i have no personal experience of supported housing or anything, but if you don't feel you can talk to them in detail, are they able to help with practical trhings like getting out or engaging in activities? i think sometimes maintaining as much of a normal routine as possible can be one of the most helpful things.