Great testing Eric, I have tried the similar test with my TaoBao esc(without drag brake) and motor 35t on a 30degree slope, seems the braking effect is not good as yours
you can use any ESC, for scale crawling, any ESC with reverse is OK but sure will lack of drag brake function or drag brake function is so weak that cant hold the crawler still on hill. I am using Traxxas water proof esc. Buy RTR you ready to go. But you MUST have reverse function. Any ? just ask.
If your ESC and Motor combo has great drag and able to hold the rigs on a steep incline, just give very small bit of throttle sec by sec and it will creep down.Also if your ESC combo doesn't have a drag brake or the motor has weak drag which can't hold the rigs, you can trim the throttle a bit to reverse when going up hill or forward when going down hill.
No matter how good your rigs is, 90% of crawling is about throttle finger control anyway
Bring your rigs out more and roll/smash/drop down a hill more you'll know how to control it