It is hard to diagnose a problem like this over the internet. Here are my best guesses to get this fixed.
1. Do a complete brake bleed using the GM TECH II or USB tool to cycle the ABS pump. This will have fresh fluid through the entire system and make certain there is no air in the calipers. Make sure both bleeders on the calipers are used. Do the calipers clamp and release evenly now based on pad wear?
2. Rebuild the front calipers.
Run this by our Dad and see what he thinks.