Self clutch bleed didn't work. This procedure in the linked video did work except had to use different size stopper, had to repeat process about ten times and then I tried lifting the pedal to check for upward play and it popped up. Yay. Did a few more cycles. Seems perfect.
Mustang clutch bleeding procedure:
That all said replacing the factory clutch fluid line with Steeda stainless steel was a success. Dealer replaced clutch at 3000, and was still experiencing difficulties clutching into gear, particularly into first without either going to fast or too slow on release. Car is nearing perfection.