I like forte, he has been inconsistant, but at least no one is stealing is goaline carries... and he is the clear number 1 back in chicago.
If Barber is playing, I'd start him. sure he'll lose some carries to choice, but he is the number 1 back. and if eh gets hot, Wade phillips tends to ride the hot hand.
given your other options, I'd start LT, you know hes going to get a bunch of touches in the game, all you can do is hope for the best and that Sproles doesn't steal too many carries