1. If the freewheel is sticking, and you can remove it, you can soak it in degreaser or brake cleaner and then lube it with a small amount of oil.

2. If the jockey pulleys are sticking the rear derailer should be disassembled and cleaned.

Test them independently to determine the problem. Also, are you sure the rear wheel was repaired correctly? Something weird could've happened there. If I understand you correctly the rear hub was cracked. If that's the case I assume it was replaced, as I've never heard of repairing a cracked hub.