I reread the OP, and I think that the changes in roles probably matters a lot. He's gone from being the experienced one and the fittest one, to being the one in the background watching you improve and gain experience, with help from "everybody else but him".

I'm guessing things would be better if he either were racing again himself, or if you could find some way to let him help you. Even if he's not on a ride (and even if you don't really need it), you can talk things through, ask for his advice, say you'd appreciate his input because he has more experience. Everybody likes to feel needed and necessary, and maybe feeling competent about racing and training is something important to him.