I hate to tell you this W., but what your son is doing is totally normal. Yes, it will help if you keep to a bedtime routine each night. And yes it will help if you make sure he's been well fed and isn't waking in the night out of hunger. And of course, it will also help if, as someone else suggested, you don't reward him by getting him up out of bed when he wakes. Another help is to make sure he is warm enough in the night -- they often kick all their blankets off at this age when they wriggle and toss. Warm blanket sleep pajamas with an undershirt layered underneath can help if you home gets quite cool in the night.
But beyond these efforts, you'll just have to breathe deep and accept that this is normal and routed in millions of years of human nature. In our culture we may think it's "normal" to plop a baby in a crib and expect it to sleep through the night a.s.a.p. the reality is that this is relatively recent social innovation.
For prior to this, babies and toddlers always slept snuggled with their parents, with mother's breast always within reach. And because mom always kept baby near, nursing on demand, her hormones didn't allow her to become pregnant again until the baby was between 2 and 3 years of age. So baby didn't have to stop being a baby until they were at least 3 or 4 years old.
But clearly you can't change the fact that you are having another baby already. So what I would recommend is that your husband gets the job of getting up with the 1 year old. You need your rest. And in the next few months that's going to get more difficult to achieve because of the new baby pushing on your bladder and etc.
So your husband is just going to have to be a Big Boy and realize he helped get you two into this situation and now he will have to do what's right and get up with the older baby.
If he is consistent about how he handles these night time wakings -- firm but kindly and loving, not getting baby out of bed, etc -- they should dwindle to once in the night. (If you're lucky and your son has a mellow temperment they might cease all together!)
If he does feel the need to give your son the bottle in the night, try having it be just water -- or at the very least, highly diluted milk. So that your son's body doesn't get used to having the food in the night. And as i said, make sure he is not borderline hungry at bedtime. A hearty dinner. A bedtime snack. Then off to bed.
Also, you might consider lighting in your son's room. Some parents think a pitch black room is appropriate, but so many children find this frightening and disorienting. A night light or a dimmer switch on the room light can help.
Be sure too that he has his special cuddlies (stuffed animals).