Babies are usually pretty manageable. They're used to being told what to do by their Mom. I'm glad you caught him before there was an accident. IMHO, They shouldn't leave a halter on him all the time and ESPECIALLY not a lead rope. Too much chance of him breaking his little neck.
I have a question about your comments yesterday about Rusty and stifle problems. I asked a friend at the ranch my son ropes at yesterday about it and he said it sounded like stifle too. He said he had a stifle problem once. He tuned the horse out for 6 months then never had a problem again.
From what I AM Understanding you to say, Rusty's problem might just be that he is not in the best shape and I could still ride just easier. Bring him back up slower???, and that might fix it???
Becky