Hi Lph008,
You're barking up the wrong tree.
It sounds like to me that you do not have a mechanical problem preventing the brake pedal from returning.
You have instead a hydraulic problem, or to be more precise a low level hydrostatic lock in the hydraulic fluid path.
Somewhere in your brake hydraulic circuitry is a blockage, caused by debris, a sticking or locked or blocked valve.
Fashion or manufacture yourself some adaptors that will connect hydraulicly to every connection point on your circuit, the adaptor should be hydraulic connection on one side and compressed air on the other. Now just like tracing a fault on an electrical circuit go to every point on the circuit until you locate the blockage.
Alternatively in place of using compressed air to hydraulic adaptors you can use a brake system bleeder then it will hydraulic to hydraulic adaptor, it will get a messy with compressed air with brake fluid being blow all over the place. Having said that it will be equal as messy with a brake bleeder still squirting brake fluid everywhere make sure you use bleed containers and plenty of rags to keep the mess down.
Best of Luck GMSAHFR