97 ford escort, weak rear brakes

I changed the front pads and rear shoes of my 97 escort. I noticed the
rear brakes are weak. With the vehicle raised, I could turn the wheels
by hand with the brakes on. On ice, I couldn't lock up the rear wheels.
Unfortunately I didn't check this before I replaced the shoes.

This car has a funning looking brake adjuster. It doesn't have a star
wheel. There is no dust cover access either. I stopped repeatedly in
reveres to adjust them.

With the rr drum off there was almost no movement from the wheel
cylinder when the brake was pressed. Since I hadn't opened the
hydraulics, and the pedal was firm I didn't think there was air in
the lines. I thought I had a frozen wheel cylinder. I replaced both
rear wheel cylinders and bled them. I can no longer turn the wheels by
hand but I can't lock them up on ice. I'm concerned that the rear
brakes aren't doing anything significant. How can I tell if the rear
brakes are working OK?

I suspect the proportional valve. Can this be tested?
BTW: The parking brake works fine. This car doesn't have abs.