If you have a baby, you're going to pull over for one reason or another. You just factor in that time. Even if you feed a newborn by a bottle, which you could do, maybe, while he's in a carseat (if the angle is okay), you still have to burp him and deal with spit up and so on. Keeping breast milk cold and then heating it up isn't that easy - you just need to have the flexibility of doing everything without you being out of your own seatbelt to feed a baby in a car seat.
Bottle choices are really individual - it's hard to know what each baby will enjoy and use. I do think he should be using a bottle at home, not just in the car though, so he gets used to it. If you can pump, it's truly wonderful for the other parent to be able to feed to, for the bonding as well as for your sleep. It's not for everyone, but if it works for you, don't let anyone talk you out of it.
We've all been where you are - trying to figure it out! It's not easy! Try to make it less about the destination and getting to a place that's 4 hours away in anything close to 4 hours. Start enjoying the trip, the scenery, the places to pull over, the calm time with your spouse, and so on. We had wonderful road trips from when our son was 3 months old (and we took forever to get where we were going!), fun when he was a toddler and an elementary school child, and through high school. We even did the auto train to FL and took 3 RV trips (one of which was the "college tour" during his junior year. If he was in a fussy phase as an infant, we just changed plans and didn't travel so much - Grandma came to us, you know?
We didn't have DVD players or every gadget either. We sang, we played highway "bingo," we had car games, and we stopped to see things en route. From age 6 on, he started to learn to read a map - we didn't have GPS then, and I think everyone needs to learn how to do this!
It's a new way of thinking from what you've been used to, but it has value!