Look up "wonder weeks." There is a major stormy period around 4 months that it sounds like your child is currently going through. Your child is going to have many periods where he doesn't sleep: when he is teething, when he is learning to sit up and roll over, when he is learning to stand. Most kids wake up all the time (my great sleeping 17 month old woke up screaming her little head off the other night and I had to go into her). So, while we don't want to create bad habits, there are many periods when they will have a crazy sleep schedules, especially when they are as young as your son.
If I was you, I'd figured out at what times you are going to feed him. Maybe you should try feeding him at 11:30 tonight and see if he then will go till a 3am feed -not the best situation when you have to get up for work, but that spacing might work --it did for my daughter (I put her to bed at 6:30). Also, I think the pacifier will just cause more problems in terms of learning how to self-sooth. Let him use his hand if he needs something, it's better than him learning to use the paci and then you having to go to him a million times a night when he loses it.
Also, keep in mind that craziness will always accompany changes in schedule, traveling, etc. A late bed time almost always results in a crazy night of sleep. So, do give yourself a break after being away. I'd give it a few more days and see if he doesn't settle down by himself.