A. It's hard to say why your son has started to throw tantrums, but it's unlikely that your trip caused it. It's quite possible that the timing of the end of the trip and the beginning of the tantrums is just a coincidence.
The three most important things to remember about screaming and temper tantrums are: 1) they're normal and all babies and toddlers will have them from time to time; 2) you need to keep your baby safe; and 3) you need to keep your cool. Understanding that tantrums are normal is what helps keep me calm, and keeping calm is essential. If you get upset too, you may frighten your baby and, worse, teach him nothing about how to manage his emotions. Think of yourself as his container -- you need to help him learn how to hold it together, and at the start, that means you holding it together for him. Talk to him in a soothing voice. Even if he doesn't understand your words, he'll understand your tone. If you can hold him, go ahead; otherwise, seat him in a safe place and rub his back.
Your son screams when he doesn't get things right away because he has no understanding of time and little reason to believe that another way might work. You can help him by modeling other methods for him and, believe it or not, by responding to his requests. For example, if your son is sitting in his high chair and screaming for the spoon he just dropped, you can say in your most even voice, "You dropped your spoon? You want me to get it? Here it is. Here is your spoon." The talking will distract him and your tone will let him know that help is on its way. Soon he'll learn that he doesn't have to scream to get what he needs. Right now it's very frustrating for your baby to have so few tools for conveying his wishes, but this frustration will decrease in the next few months as he begins to learn more words.
It's not unusual for babies and toddlers to hit themselves sometimes. Often this has a self-soothing purpose, not unlike rocking or head banging, and if it doesn't continue into the preschool years and regularly cause injury, it's not a problem. (Of course, if you're concerned, you should check with your pediatrician.) Don't be alarmed that he gave himself a bruise -- your little Tarzan just doesn't know his own strength!