Cap OD for a 7290 Yoke is 1 1/8 inches, for the 1350 is 1 3/16 inches. on a 12.5 sec 3600 lbs car is the step up worth it?

I think a 7290 is plenty good for mid twelves, and a lighter shaft will only make your wallet lighter. I don't think you will see an ET improvement anywhere.
I did build an aluminum shaft with 1350s on both ends, and billet yokes, but that was for a car with a transbrake and 14/32s.
I guarantee your tire swap idea will have lots more effect on 60 ft. Gearing (shorter tire) will help if it's the right direction, a lighter shaft will do nothing.