2007 mustang front brakes replaced now front passenger tire is wet on back side and brake pedal is spongy and low brake fluid after putting in more brake fluid

Your Mustang either has a leak at the brake line, split or leaking at the fitting that attaches the line to the caliper, or you have a brake caliper leaking fluid.

Wheel cylinders are on drum brakes. They haven't put drums on the front in decades. Fronts have disc brakes. Take the wheel off and have a buddy step on the pedal to find the leak and repair or replace the appropriate part