1-If he drank milk from a bottle it seems weird to me he'd dislike the taste now??? Did you do anything differently; warm it up or anything in the bottle? Just seems odd to me.
Nope, we did nothing different! I was stumped, too. We tried it in a sippy cup for a couple of months afterwards, but he just wouldn't drink it. So, it must have been that it came from the bottle. Honestly, I'm not concerned that he doesn't like milk, per se. I know loads of people who don't like it/drink it. So, I'm OK with him not liking it. As I mentioned, he will sometimes want a sip of milk from my cup, but will only take one sip. I ask if he wants more, and he says, "No."
2-If chocolate milk gets him to drink it, I think it's a good idea, but there are ways (as discussed above) to get the sugar content down and pack more vitamins in there.
Yes, this is the approach I was contemplating going with. Not a full recommended serving in his milk.
Heather, I like what you said about only offering it maybe once a day. That's how we are with juice atm. He only gets it for breakfast, though he asks for it all the time

Nicole, this is what I meant...I know I'm the parent and can hold my own against a tenacious toddler. I just don't want to open Pandora's box even more to hear the constant asking for chocolate milk, lol!
Thanks for everyone's responses and for letting me bounce this idea around (more for myself than anything). I think we'll try it out sometime over the next couple of days and see how he does.