Kazza I am so sorry it is so tough.
I don't think the behaviour is normal and I think you are right to be worried. I think you are right to shout as loud as you can for respite or help or whatever.
One random thing that jumps out at me is that your son doesn't call you mum, and this is distressing to you. I can totally understand it. I mean I can understand why it is distressing.
I wonder if he is withholding this waiting for you to snap and act mean so he can feel justified in not calling you mum?
Do you and your dh have time apart with the boys, one on one, per child and then swap etc? And do you have time to just the two of you?
Can you do any activity with your older son that is artistic, or requires some sort of focus, some activity he might be good at but need to learn and you can learn with him? This is as well as all the other stuff.
Can I also check if you have had any assessment re ASD or ADHD or anything and also if any other factors are there such as bullying at school?
You said you and your dh analyse everything that is done in the day, do you think that maybe you need to lessen off this and focus on a few areas.
It really is very hard to eat the whole elephant in one go, as the saying goes.
Lastly, is there anything at all in the 11 months that has been fun or nice or good that has happened with ds1? Can you think of any good memories, find the photos of any nice days. I feel he is in there somewhere but he is making it so hard for you, because it was so hard for him. No one is judging you, we are all here for support. You are trying so hard, I hope and pray you may find strength and break through