This is why I have been confused, since the beginning, as to why you didn't aim for the usual theurge requirement pattern and ask for 3rd level (or thereabouts) in each class. Personally I would have chosen to go for 'Ability to cast 2nd level arcane spells and ability to use 2nd level infusions', which does drop the power rating a little from one side, but bolsters the other and keeps in line with just about every other theurge PrC I remember seeing.
If you're dead-set on using the practiced spellcaster approach, you first need to brew a re-wording of the feat, and present it above the class AND in the requirements, otherwise this only really works for Art.5/Wiz.1
On the bright side, once this scrubs up and re-words for clarity and concise phrasing, I think this could work nicely. You still need to fill up the level 9 vacuum, did you dislike the other suggestions or do you have something bubbling already?