First of all, congrats for keeping your son RF for this long. He has been so much safer than if you had turned him at a year! If possible, it is best to put your safest seat (rear-facing) in the least safe position (outboard), and your least safe seat (FF) in the safest spot (center). Our baby bucket seat and our RF toddler are on the outsides, and our FF preschooler is in the center seat. All three are in one row in our van, because that's easier than trying to buckle from the back of the van. My oldest just ducks under one of the other seats to get in.
Rear facing is much safer than forward facing. In a side-impact crash (the most dangerous kind of crash), a forward facing child is 5x more likely to suffer a fatal injury. This is true across the board, regardless of the passenger's age. Even adults would be safer rear-facing, although that would make it kind of hard to drive!
As far as him being squished RF, have you taught him to cross his legs when he's in his seat? This really helps my monkey. Also, little ones are actually comfortable on a long car ride when they are rear faced - forward facing, their legs are hanging off the seat. If you have ever sat on a tall stool for a while where your feet couldn't touch the ground, you will remember how uncomfortable it got, and how your legs fell asleep. If you have a Boulevard, you can forward face it pretty quickly (and I think you can adjust the straps w/o rethreading?). Maybe consider starting the trip RF, and if he seems to get uncomfortable that way, then stop at a rest stop and turn him forward facing.
Once he's forward facing, I would put him behind the passenger seat. My toddler always kicked my seat while I was driving, which drove me nuts! I guess I'm not seeing the problem with having 2 door entry (although I'm at the point where I *have* to). If you set the baby seat right next to you while you fasten/unfasten your son, what would the problem be?
Best of luck,
S. L