Re: Sucking to soothe?
Yep, I'd flip him to the other side to comfort nurse. Maybe it will help with the breast preference. I'm guessing you're hitting (or about to hit) the 3 week growth spurt, in which case you might want to just let him nurse as much as possible to get your supply where it needs to be.
All that said, I think you'd also be fine to offer him a pacifier once you've offered both breasts and you're sure he's not actually still hungry. Both my kiddos took pacifiers from day one and we never had any problems with supply or nipple confusion. If you were having latch problems or supply issues I'd probably give you a different answer. But since things are going well, I think you'll be fine.
“We are not put on earth for ourselves, but are placed here for each other. If you are there always for others, then in time of need, someone will be there for you.”