The possibilities frighten me and excite me at the same time.
Add to that that you'll learn a shared vocabulary and 'way of thinking' which will allow you to communicate better with those connections.
So if you want to know what to study, just ask yourself which company of graduates you would like to belong to.
It'll also help with that sense of identity you felt you were missing.
1. Don't get paralysis.
2. Pick something that gives you good career options. The rest are your hobbies (and it's good to have hobbies).
4. Be cautious taking on any educational debt -- make sure it's worth it.
Your career will take many turns but you want your opening move to be strong.
Frankly, if you can program and enjoy math, your future is bright. When you love your work, you won't need the escapism of substances.
I believe most institutes allow you to change your course(s) and even transfer over to a different program altogether.