Your rule of "no fountains" is going to have to be bent in at least one case, perhaps two. Without touching the Foutain of magic in the Adept quest, you will never be able to attain Master Air Magic. Without Master Air you will not be able to Master Bow or Plate nor complete the Ched Rhinn quest unless you are fantastically lucky enough to find enough fly scrolls or a Fly spell book. Since you cannot enter the Air Guild, you cannot buy one. (I have never been able to get to the appropriate people in those three places without flying). Without touching the creations font, you will never be promoted to Elder Druid - none of these except Chedd Rhinn are game stoppers but certainly a big loss in XP and reputation.

Chedd Rhinn must be completed in order for the Seer to give you the next quest so it is a "main line" quest.