Thaumaturgist doesn't really mix very well with malconvoker in my opinion, since you want augment summoning much sooner than 9th level and the other abilities are only decent. I'd replace it with another PrC personally. One of the other possible issues with the build you had is that your level for rebuking undead will be very low after you start thaumaturgist and malconvoker.
I think you might really appreciate the Master of Shrouds PrC though - it's one that focuses on summoning incorporeal undead, and it also advances your rebuking level. At the risk of being conceited, here's my guide to the PrC:
http://brilliantgameologists.com/boards/index.php?topic=3310.0As for feats, I'd trade out Nimble Bones and Spontaneous Summoner for something else, maybe some metamagic like Quicken or Extend/Persist. A lot depends on how many CLs you sacrifice for PrC power though.
Good luck!