The best thing you can do is put him straight into his own bed. Make it a huge deal, let him pick out his own sheets and make it a big boy bed. I got twin beds for both of my kids and put them in it at 18 mos and they did beautifully!!! They were so excited. I got a bedrail and it gave them more security.
Unfortuately hearing you say with a a toddler now and you don't do "crying it out" I am confused. What do you do when he pitches a fit? I would assume you don't give in or coddle him then. It is a transition to move into his own bed but he will handle it much better if you just make a plan and stick with it. He will be looking to you for reassurance this change is a good thing, if he sees you stressed or caving in then it will backfire. I don't think letting him scream for an hour is productive, however he may cry, you need to be tough and stick firm or each time he cries hard enough he will assume you will just give in, that goes with a number of things. At his age he will be getting much more peaceful sleep out of your bed!!! You and your husband deserve to have your own private place.
I never did crying it out until my kids were one year old, after that it can just become a power struggle and running in and picking them up, or rocking them or nursing them to sleep is so counterproductive for them and confusing. I would make sure there was nothing major wrong, did our routine, walked out of the room. I did not go back in until the 15 minute mark then made those increments longer, however I didn't have to even do it more then a few days if we had problems.
Toddlers don't always get their way and they get mad or upset. It isn't being a bad parent sticking to your guns and it will be a process, not overnight but you cannot give in either.
Start at naps and lay him down, get the room like he likes it, help you decorate it or whatever. Get a chart down so he gets a smiley for every big boy night he has.
Start even with a mattress on his floor, lay there, read, snuggle and empower him. But walk out after exchanging good nights. He will be fine. Put a baby gate on the room if you are concerned about him getting up. Sleeping on his own is a gift you will be giving him and doing all this now before the changes of a new baby will help everyone. He should not be nursing to sleep or needing you or your husband in the room to sleep, that is so hard on them and the best thing is just to decide to do it and stick with it, he will adjust quicker then you think.
You should think about weaning him now too or that is going to cause you a different set of heartaches as newborns need the breast milk but at your son's age he doesn't really and if he is using you to fall asleep he has no idea how to self soothe, you would be doing him a great service to help him wean now. When the baby is born he won't and that is going to be confusing for him.