Having worked at hospitals, I can tell you that folks on their deathbeds almost NEVER regret things they have done--they regret what they didn't do.

I would admire you for going back to school to up your employment. I would admire you for not settling.

As for your list "Have too high degree to be student again"-- I know folks who have three and four degrees. There are no rules that day you can't go back for another.
"Should have completed..." Don't 'should' on yourself. That was then--this is now--and now is all we have.
"Too old" again, there are no rules for ages in college. I've heard of 80-year-olds getting a degree! And I admire them.
"Don't have full time..." while in school, it would be best if you didn't work full time. As you know, school is a full time job--

My vote? Go for it!