I am sorry things are so difficult. I used to have a tough time getting my children's attention. I hated being yelled at so I found a way to get it that involved something they liked. It was strange to other people, but it worked. I used dessert.
Yes, you read that right. If I needed my child to stop something and listen, or to do something else, especially when electronics were involved, I would say something like "chocolate chip cookies" or "chocolate pudding".
It all started because I noticed I could be talking to anyone about anything and my son would not notice anything but if I mentioned ANYTHING about a dessert, especially anything involving chocolate, he immediately knew. Often he thought I had promised him chocolate even if I had just mentioned wanting something chocolate for myself. I decided to use this rather than just being frustrated by it.
When I started it, I gave them the dessert item EVERY time I mentioned it. Then after about 2 weeks I gave it every other time for a couple of weeks, then it was on an irregular schedule so they never knew when they were getting the dessert. If they didn't pay attention to it, they for sure were not getting it. It may seem counterintuitive, but an irregular pattern of rewards is the most reinforcing pattern, so this really works for long term success.
I used this for a decade with my kids and it worked. It was almost a joke in the family by the end, because it could make the kids laugh, and of course my parents thought it was hilarious, but they also thought it was genius. Of course at first they thought I had lost my ever-lovin' mind, but what did they know? I had one child who might physically attack me at the end of a movie or if I turned off a video game because we had to go to do something or it was time for bed, even if he had been given warnings and all those things the therapists told us to do. Chocolate chip cookies or Cheesecake or whatever dessert was his favorite at the time worked a whole heck of a lot better, especially after a couple of months when I only had to give it to him a few times a week!
Find his favorite thing, especially a portable thing, and make it your commodity. Use it as a reward for transitions the way I used dessert foods. Heck, use dessert foods if he loves them.
My other suggestion is that if what he is becoming so verbally violent over is video games, then eliminate them. Just take them away completely because he cannot handle them. If he is so unable to handle himself when asked to stop using them that he behaves that way, he clearly cannot continue to use them. I did have to do that with my son at one point. He just did not play video games at all. I would not allow anyone to treat me that way. We did not play video games as they are fun but not a necessary part of life. It eliminated a lot of confrontation. The first couple of days were awful, the rest of the first week was bad, the next week wasn't fun, and things just kept getting better from then on.
I was shocked at how much imagination came into his world in the weeks after we took his screens away. It amazes me how screens really do impact imagination for our kids. I wouldn't suggest taking away all screens for your son, just the video games at this point, but if he is aggressive over limits on using other screens, it is something to think about. My son lost screens because he kept getting aggressive physically over time to stop using anything with a screen, even in school at the end of class. It was a real problem, but not one you are facing right now.
You can try re-introducing video games after a month or two, if you feel that is enough of a break and he is ready for a limited trial. Explain that if he is yelling at you when you tell him it is time to stop, then they will go away again. It isn't fun being the one to take things away, but these are not things that are essential, or even things that are beneficial. There are tons of kids that don't play these games and grow up just fine. No matter what your kids tell you to the contrary.
I hope one of these ideas helps.