Thank you very much! I think I'll just add 2-3 to the base Purchase DC. As for the spell making, I followed your advice and made a rip off feat of Scribe Scroll.
Weavery [Magick, General]
Your mastery of magick has advanced to the level where you may create your own, unique spells with rigorous research and no small amount of effort
Prerequisite: Magick Mastery, Knowledge (arcane lore, for the First Practice) or Magick (for the Second and Third Practice) 9 ranks
Benefit: You may create a spell of any level you have access to. Creating a spell takes a number of days equal to the spell’s level. The purchase DC for the
raw materials to scribe a scroll is 15 + the spell level.
You must also spend experience points to create a spell. The XP cost is equal to the spell level x the purchase DC of the
raw materials.
Finally, the Mage makes a skill check (Knowledge [arcane lore] for the First Practice or a Magick check for the Second and Third Practices). The DC for the check is 20 + the spell level. If the check fails, the
raw materials are used up and time wasted, but the XP is not spent. You can try creating the spell again as soon as you purchase more
raw materials.
Special: Consult your GM when using Weavery.
Again, thanks for you input; it helps out a lot!