Hi! Welcome to car-seat.org.
First, I have an 07 4-door and the airbag sensor is pretty sensitive. Mine goes off with my bag from the library on it, but would stay on the one time I had to transport 4 kids and put a child in a car seat up front. I also wouldn't want to trust a sensor to stay off with a child in the seat. If the child is close in weight just holding a cup full of water could turn it on, or resting your hand there, etc. You can try to go through the red tape to get your airbag deactivated, but you have to petition NHTSA, wait, wait, and wait some more. I'll try to dig up the link for you later. The best option is to not use that seat for a child. Even if it wasn't for the airbag it's not the best idea.
Second, you say your 16 month old is 35 lbs. Are you sure? It's for sure possible, but that's on the heavy side for a 16 month old for sure. What seat is he in now?
I'm sure you're not going to like this, but the safest place for your "buddy" is in the back. My 2 year old is his Daddy's buddy too, but he rides safely in the back seat of Daddy's truck. (The Jeep is mine.) They go work together, drive the tractor, and all of that, but he won't be in the front seat until he's a teenager. Just how it is. Your son is also young enough that it would be better for him to be rear-facing, but forward facing in the back seat with a top tether and correctly installed seat is acceptable and still meet the safety minimums. Your front seat doesn't have a tether anchor (TA) either, which makes it an even worse choice. The TA helps keep the seat and child's head from hitting the interior (dash in front) in a collosion. It also helps keep the child in place if the airbag would deploy. **note, never, ever put a rear-facing child in any seat with an airbag. It is deadly**
The back seat is split in the 08 two door, right? I'm pretty sure it is. In that case the best coarse of action would be to put your son in the back, and buckle some extra gear in the front. This is what I did in our 97 two door when we just had one child. We went off roading a lot then and she was always in the back and stayed rear-facing till she was over 2. She loved facing backwards- especially when the top was off- and was sad when she had to go forward.
I hope that answers some of your questions. I'm sorry it's probably not what you want to hear, but we all want your little guy safe!