1. Don't over do it.
2. I'd say so.
3. 80 is good. Won't hurt to work on it though.
4. That depends on lots of things. How old you are, etc. I see you have not been active for the last 6 months, I'd say a year before you could enter a race and be competitive. Of course you could enter and get dropped...
5. Not that I know of.