I will say that the spellcraft aspect becomes irrelevant fairly quickly. 1st level, DC is 16... meaning take 10 if you've got a +4 from Spellcraft and +2 from Int. 2nd level spells, the DC goes up to 17... but at 3rd level, you have a +6 ranks from Spellcraft, and so need only a +1 from Int to take 10. 5th level, you've got 3rd level spells, so DC 18... but you've got 8 ranks.