Those are some really great ideas!
That's also exactly what I mean by "making yourself happy" ... i.e. only trying to control things that are in your power to control.
I think you'll find that once you start taking care of yourself, the universe will take care of the rest of the details.
You asked for suggestions to increase your mental abilities. If it's within your financial and scheduling means, I would suggest taking a University or College course. Any course, anything that interests you. Calculus would obviously be a good challenge, but if you're not interested in calculus then it will be very tedious, difficult, and hard to find motivation.
Reading is also a good way to stimulate your brain, especially non-fiction.
I'm a big fan of logic puzzles. You can get those magazines full of them, and do one or two a day. Crosswords and Sudoku also challenge your mind, but they're not for everyone.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker