When you have a blended family you have to do a lot of compromising and letting go, and whether or not you’re insensitive and your husband is unreasonable is beside the point. What you need to do is make this situation work.
Get out of the power struggle you and your husband are having over your children. Your son has his own car, so why create a big to do over his not being allowed to drive the newer SUV that you and your husband own. If your husband doesn’t want your son to drive the new SUV, then let it go. Don’t get into the details of whether or not your son should or shouldn’t be paying for maintenance, or gas as a condition of using the new SUV. Just let your son drive his own car, and if he needs to borrow one of your cars, let him use the older car. Don’t make an issue of it. Roll your eyes, laugh about it, and understand that everyone has their quirks. Don’t look for a fight where there doesn’t need to be one.
As for your son’s driving you to the airport, take the older car so as to avoid a fight with your husband over something inconsequential. Being squished in a car for an airport drive is a far lower price to pay than having your family fighting.