Given the probably cost of the Ti bolt for the crank or the innertubes.
Then a Ti bottom bracket and Light Quick Releases is an obvious weight reduction step, drop the brake dust covers too, and Ti axles for the pedals ;-)
You're missing the headset locking-washer. They are in there for a reason.
and a good round of Alu bolts (STI shifters, rear mech brake away, mech cable clamp bolts, front mech clamp bolt, bottle cage bolts etc. (or plastic ones/push in for hole fillers like the other cage bolts holes), chainring bolts...