Well, if you're burning a feat on Spiked Chain i really recommend the "Shadow Blade" feat (well, for TWF too, as long as you're using Shadow Hand weapons (dagger, sai, short sword, spiked chain, siangham, and unarmed strike))
it allows you to add your Dex to damage rolls with shadow hand weapons as long as you're in a shadow hand stance (if you do that i'd recommend to swap your str and con stats)

and on tripping: look at setting sun maneuvers, that's tripping (even based on dex instead of str) and damage dealing in one