Normally that spring is a wrap around at the end of the cable where it attaches to the lever. They can be a bit fun.

How much brake material is left on the shoes? Same for the front pads?

I had similar complaints with my brakes also, along with the mentioned recurring need for replacement springs. I replaced rear brake drums and shoes, realizing that someone had cooked the rear brakes by leaving the parking brake engaged at one point. That resolved the repeated brake hardware failures, but the pedal was still low at that point. It wasn't until I replaced the fronts soon after when I ran out of pad that they began inspiring confidence.

Do a full check of all brakes and brake lines, looking for corrosion and leaks. There is probably no harm in doing a brake flush also, or at least bleeding them with fresh fluid.