Juice is NOT bad for kids. It's how much you give them. 4oz is a child's serving. And only 1 serving per day.
For an adult it's 8 ounces per day. When you over do anything it's bad for you. If you do it like it's supposed to be done you are just fine.
I agree that he might not like sippy cups. At 21 months he should be using a regular cup anyway. Have you tried the take n toss with the straws? Our kids used those and if they lost them or chewed them up it didn't matter. They are less than fifty cents each.
This is the only kind of cut I would let the kids have a drink in when they were not sitting at the table.
If he really didn't like any sort of nipple except silicone then he is picky and might have some issues later on with different foods. It's not a big deal for them to be picky. He'll eventually outgrow it.
If he's still on the bottle that is also okay. If he isn't holding the bottle in his mouth all night then he's probably not going to have any dental issues from the bottle.