With your feat tree I would still need 15 dex, it is a requirement for TWF. I would also have to eat up an extra feat to be able to wield a meteor hammer.
I cannot find a feat called dirty fighter...there is Dirty Trick Master...which is banned in PFS. There is a trait called Dirty Fighter, which does not seem to apply as you have to have a consistent partner to fight at your side. Or Dirty Fighting, which only applies if you are flanking someone...which I probably wont get to do much of in defensive stance.
Going for a trip master is not the direction I was thinking. I am thinking more stone wrecking ball.
Dirty fighting also lets you qualify for feats:
Special: This feat counts as having Dex 13, Int 13, Combat Expertise, and Improved Unarmed Strike for the purposes of meeting the prerequisites of the various improved combat maneuver feats, as well as feats that require those improved combat maneuver feats as prerequisites.