UA's inventory for TK shows sufficient award space (assuming that is correct). I don't have enough miles to book the same itinerary and cancel this one. I can try to cancel this one and rebook, but risk not getting that same level award (30k) on the UA SFO-CDG segment (shows 70k now).

Would cancelling segment 2 & 3 (the segments on TK) and then trying to add them back work? the other alternative is just to cancel the one passenger who is not confirmed and have them book separately but that is a bit more complicated and still run the risk of not getting segement 1 at the lower mileage cost.