I agree with what everyone has said about OTTBs, they are THE best horses and I've only owned OTTBs.
I started Second Chance to take freshly retired OTTBs and retrain them. So far we have trained and rehomed one, Eddie. I do have another gelding that we are training, but its becoming very hard to let him go. He's only 5 years old, already been through two auctions before I picked him up, he had a decent race career before he was just discarded. If you wanted, we could find you a horse and restart it. If you're interested in this, PM me, and we will get to work finding what you want.
To answer your questions, yes its normal for an OTTB to go "bonkers", same with any young horse. You do have to remember they are still immature. From my own experience, OTTBs are not hard to train. I've had nothing but horses with excellent work ethics.