Ok, so the diff binding is due to the spider gears. I used the rear differential to troubleshoot. Took the rear diff out and switched components from the front to rear diff one by one to isolate the problem. Not diff outdrive shafts, ring gear, diff cup, or spider gear cross pins. It was the spider gears. I've got new spider gears on the way.

Tested the mesh between pinion and ring gear per your suggestion. Found only smooth movement and no play in the pinion depth.

Put the front diff back together with the good spider gears from the rear just to test it out, powered up, and no movement on the front wheels. Came to realize that I only needed to do some better basic observation to begin with, that the front drive shaft is not moving! Problem is not really in the front diff, pinion, ring gear at all!! So, must be something in the center transmission. Maybe it's the same problem smanders had as shown on his youtube vid with yeti xl at the track. He also had knocked out the front drive with some kind of center transmission issue. Thanks for all your help with this! I'll report back later when I find out the culprit...