I'm taking classes in mid-50s. Never too late, and regardless of the anti-college faction on HN, I think it's worthwhile. Mathematics in particular will be useful in many places you might want to go. As a hiring manager, I see someone doing this as a positive; I value folks who seek to improve themselves.

Your plan (CS local for CoL, Masters elsewhere) seems very sound. I don't know any companies subsidizing something like this unfortunately. However, when it comes Masters time, depending on where you go in the world there will likely be financial aid options of various types and quantities.