I almost hate to jinx it, but I think there might be some progress in the "teach Tip the formal obedience retrieve" front. I reread the inducive retrieve instructions, and realized I had not been doing it exactly as they said. so yesterday, I did exactly as the directions said: put dumbbell in dog's mouth, praise, release, and reward. Reward was liverwurst. 3 reps of that then breaks for a bit of heeling and try again. do this 3 times. By the end, Tip had a look of dawning comprehension in his eyes, and was no longer trying to force the dumbbell out of his mouth.
Today, we tried again. Tip started to hold it, and I kept the dumbbell in his mouth for a second or two before having him release it. and he started to try to hold it.