@abientot
I have trained people before that had your background and went on to do what you want do. Nine out of ten times you will need a degree in Psychology or Criminology or something similiar. If you go with the Open University, they will have no formal entry requirements (but make sure you choose an accredited course, not all of their's are - it needs to be BPS accredited for psych). Other option could be Arden uni (UK-wide but best in England) or the University of Highlands and Islands (also UK wide but easiest if you're in Scotland). These places are also prepared to start with the very very basics and used to people from more diverse backgrounds than your standard teenager fresh out of school. I even had mum's doing courses on maternity leave, i.e. with a newborn. It is really hard with a child at home but can be done.
All the math in psychology is stats and - much to my dismay but good for students' marks - the standards for understanding it are pretty low. If you do it full-time, you should be able to get student finance and a council tax discount. If your depression is well-documented in your medical files, you might also be able to get fees paid if you are studying part-time but I you'd have to speak to the uni of choice to find out.
The police is generally very keen to recruit psychology graduates, although you would have to work your way up from the bottom regardless of the degree (but it would move quicker). The police and various army-type forces (RAF etc. - I can never remember all of them) also tend to pay part-time course fees for their staff, so you could get a job there and have them pay for it. The unis always offer a graduate advice service (help with applications, interview prep) and networking services (contacts to alumni, events,...) which makes finding a job easier.
Becoming a profiler is next to impossible but only next to. A) it doesn't really exist the ways it is potrayed in crime shows, B) the few jobs that are like it are very competitive and usually require a Doctorate. Going into research could be an option, though. There is usually funding for Forensic research but it can be tiresome, as ethical approval often takes up to a year - it is all quite complicated. Sidenote: Research has repeatedly found that rather than school marks, motivation is the most important factor when it comes to how well students do on a degree. So if this is something you really really want to do, I would consider it. If this is more a "this would be nice", it might not be quite right.
You could also look into Forensic Psych but be working as a Forensic Psychologist always involves postgrad degrees, many (but not all) of which require in-depth understanding of algebra. Unis either have their own counselling services or have contracted a distance counselling services, which you can use for free throughout your studies - if you are prone to depression, thar could be helpful. If you can provide a confirmation of mental health problems (e.g. from your GP), you can also register with their disability services and ask for reasonable adjustments, e.g. if you need a longer than normal extension.
Don't go for data science unless you have plenty of programming experience already. It has become very competitive and salaries at the entry level have dropped quite a bit. That xperience they are referring to are internships, usually unpaid.
What might suit you, too, going by what you have said, is law. Either as a paralegal or lawyer in the area you are interested in. Mostly paperwork, relatively little contact with clients and it pays well. You can choose an area that would be relatively close to what you are interested in.
Last but not least, apologies for any typos - I woke up at 5am and the coffee hasn't kicked in yet. I tried, though!