I'd recommend getting an OOC thread, Ben. I've done the other option before, and a lot of pages wound up getting spent doing nothing but talking, to the point where regular summaries had to be made about the latest developments in the RP because it was so difficult to read through it all...
uuugh lots of editing... do more later... still Sul's going to be fun to play
Er, your Strength should be 16, not 15. ^^; At 15, you've got one point left unspent for your attributes. The original spread, before racial adjustments and level-based stat increases, is 12, 12, 18, 8, 10, 12. +2 each to Strength and Constitution from being a Warforged, and then the level-based increases go towards Dexterity and Strength.
Anyway, for the feats, I'd recommend replacing Blade Opportunist with Melee Training, and then if you want Backstabber, you might find it better to replace Two-Weapon Fighting with it, and trade in one of your two weapons for some more equipment.
Also, now that I think about it, since I provide the entire party with a +2 bonus to initiative, you might get more mileage out of Quick Draw, rather than Improved Initiative. It's only a +2 Initiative bonus, rather than a +4, but you also don't have to take any actions to draw your weapon, which can definitely come in handy.