1. Other characters taking Geomancer for poison dart or Contamination would help. Fane himself taking Necromancy would indeed help him self-heal.
2. Build other party members to suit your own party. All characters are capable of switching their build to anything you need. The only fixed things to take into consideration are the racial passive Talents, racial passive Civil Ability bonuses, and racial/unique skills.
3. Yes, you can do a complete rebuild, as many times as you want for free - but only after you finish Act 1 at about level 8 or so.
