1. Yes - if you win points in any week, then those points disappear at the end of the same week the following year
2.No difference - it just means it is the 7th Futures event in that country during the year (F1 = 1st futures in that country in the year)
3. Until you start playing ATP events (ie not challengers / futures) then you won't get race points anyway. Your ranking is determined by your entry ranking, so concern yourself with that one. The race ranking purely determines whether you get in the Masters Cup - but at the end of the season, the race rank will generally = your entry rank anyway
4. Yes they retire - either at a set time (if Manu programmed them to retire in a specific year) or when they get too old and rubbish!
5. Depends how good you are / whether you want to fight for the top ranking - if so then go with the top levels. If you want to dominate fairly easily, then choose the lower levels. Up to you!