1) is fine, but 'onto' is more common.
The common way for 2) is "He is forty years old." If he was twenty and you said "he has aged 40 years", then he is now sixty (or has aged as if he was). For the former meaning, you could say "He is forty years of age."
For 3), you should say "...for the rest of...", and the 'any' is redundant.