It's hard to have a toddler screeching right beside your bed that is for sure but you need to put an end to this one way or the other! At 18mos the bottle at night can go. A bottle with water can go in the bed and that's it until breakfast. Once the good stuff stops coming he'll probably stop waking for that one. but he's going to have a fit at first I've no doubt. 6am is tough since he's probably ready to get up but if you didn't have the 2am issue then 6am is going to be a lot better!
If your husband isn't willing to do anything that will have your LO cry, then I'd move to another room. You can look after the newborn and your DH can look after the 18mos old.