OP, I feel for you! Boys are so difficult for moms: they go from being these lovely, sweet children to being surly, unwashed, and hostile overnight. Based on your post, I think you are approaching this in the exactly wrong way (and the majority of advice you are getting here is too).
I grew up with several younger brothers and have raised several boys myself. As I’ve watched my mom and my friends, as well as myself, deal with the male adolescence, I’ve seen that our usual instincts for dealing with someone who is being cruel or unkind are precisely wrong for coping with teenage male hormones. Many women will insist that their son apologize for being mean and will talk to the child about how his mean remarks make her feel bad and upset and hurt. Obviously, we all want our sons to have empathy for those who are weaker and thus it seems like sharing our feelings about their unkindness is not only right for salvaging our relationship, but also for creating a young man who is empathetic and kind.
However, most boys who are being nasty to their moms are doing it for a combination of reasons: both because they are beginning to have sexual feelings towards the opposite sex, and their mother‘s gender identity really scares them: they feel tremendous love and affection for their moms, but expressing those feelings seems terribly fraught in relation to their emerging sexuality. Add to that the fact that they are beginning to realize that Mom has a sexual identity as well. The put downs, the sarcasm, the cruel remarks: they are all helping boys to manage new and unfamiliar feelings. Overtime, of course, they learn to distinguish between ordinary parental affection and sexual feelings for others, but at first, it is incredibly hard to cope with. So they push their moms away as hard as they can.
The second reason that they do this is because the fact of Mom’s fragility and mortality is starting to dawn on them. The cruel remarks are tests; they want mom’s responses to prove that she is sturdy and resilient, that if they separate from their moms and turn to their dads as models of masculinity, their moms will be just fine! They want to know that they don’t have the power to destroy their moms, so they keep testing and testing in the hope that she will prove to be resilient and tough. That is why the best response to these cruel and hostile remarks uses humor to assert mom is still the adult and still in control (a poster above, the mom of several boys, gives great examples of this technique. “Mom is such a stupid dancer!” “You betcha kiddo—I’m planning to chaperone the school dance next week, so I’m getting all my best moves ready, just to humiliate you!” ; “I hate you! You’re the worst dressed mom ever!” “First, I love you, even when you are unpleasant. Second, don’t you know that I am deliberately tormenting you by being as uncool as possible? Wait till you see what I have picked out to wear at your soccer game next week!!”
I have seen so many boys and adult men whose moms act hurt at some action they have taken; they feel frustrated as well as terrible for hurting her; mom’s expression of hurt makes them angry; they lash out; she is more hurt; and on and on the cycle goes. Humor signals to them that they haven’t hurt you in their efforts to separate from you—and those efforts seem necessary to them because they are awash in unfamiliar sexual feelings that they have no idea how to manage.
When I was in my 20s, my youngest brother was 12-13. My parents took him on vacation with them, and he was a nightmare to deal with. I think it is no coincidence you are on a vacation: vacations push families together even more than usual—you are together 24-7, in small living spaces, etc. For a boy just beginning to deal with sexual feelings, that kind of enforced intimacy is really overwhelming, and the result is hostility. I met my parents and brother on one afternoon during their trip; I was wearing jeans and a fitted t-shirt, nothing immodest, but the fact that I was a woman was very evident. At one point out of the blue my brother muttered “whore” in reference to me. He looked as startled as I was! But I think he was just overwhelmed by adolescence and stuck in a car and hotel rooms with his parents and no time to be alone and decompress.
I hope some of this resonates and is helpful!! Don’t worry too much—it gets better!!