It sounds like our boys have similar personalities, mine was 17mo when his sister was born and he struggled in the same way.
Do you have a double buggy? If not, it is very, very worth having one. It will be your 'co-parent' - an effective way to keep everyone safe and enforce boundaries. It also helps you to get from A-Z without too much hassle.
Does the baby wake up later than the toddler in the mornings? If so, use that as quality time with your toddler, just the two of you.
If you give him 30mins focused time it might satisfy him for the rest of the day. Doesn't have to be the mornings obviously, could be when the baby naps.
At 2.5 I would just bin off the naps completely. The stress of trying to get them to nap isn't worth it.
I can’t read anymore, can’t listen to my earphones, can’t speak to people on the phone
I'm afraid this is just going from one child to two, say goodbye to those things for awhile, it's just not the season - you'll get it back in a couple of years. It's more painful trying to hang on to things like this. Ditto going to the loo on your own.
You are right in the thick of it now, it took me 6 months to really figure it out with two. You will get there! It won't be like this forever. Your son will get used to things. And you are not a bad mum!
One day, your baby will start sitting up, and you will catch them playing together for the first time and it is the best feeling in the world.