You sure about being DEX based? STR gives a lot more damage, and (especially with Abjurant Champion), you have the Shield spell for the shield AC. RAW, I believe, you could use the Shield spell for Shield Ward. (Isn't Shield the equivalent of a tower shield? Or am I still thinking 3.0 on that?)
Even if you really, really wanted to stay DEX based, at least got for an Elven Courtblade: Finessable, and twohanded for Power Attack & Wraithstrike Galore.
I really, really, don't see the point of going finesse. My first gish was that way, and he was seriously underpowered.
Also, drop Combat Expertise, unless as a prerequisite for Improved Trip.