Back to the brake lever.... as I said, I've tried it and thought "great," only for it to return to being less firm pretty quickly. I read an explanation of why this is somewhere, but don't remember the reason. One thing I'd suggest trying is to perform another bleeding session immediately after you've released the lever. That may be effective.
I came across a trick that helped me bleed a car that was giving me trouble. Use a long bleed hose and raise it above the master cylinder. Once the fluid level is above the MC secure the hose and leave the bleeder valve open over night. The idea is that the air bubbles will rise to the highest point in the system. Some bangs here and there with a rubber mallet might help move things along. This did work for me, but I worried about how much moisture from the atmosphere was being absorbed through the open line.
I just rebuilt my rear caliper, replaced the pads and bled the rear- easy. Next are the fronts, which I anticipate will be a challenge to fully bleed, as usual.