ps read this so that you believe it 
"I bluetufty (say your real name!) do not need MrBluetufty's approval to end this relationship. I don't need his permission to end this relationship. I don't need his understanding to end this relationship' I don't need his blessing to end this relationship'. It is my absolute right to end a relationship that makes me unhappy."
Please humour me here and read that out loud to yourself (saying your own name!). Read and do it FIVE TIMES! HUMOUR ME HERE PLEASE.
Then, when you've done that, practise saying out loud in your head what you will say to him when you tell him it's over. Imagine him responding and imagine yourself NOT justifying, explaining, defending your decision.
Get your own stock phrases that can't be argued with.
Read these out.
I do not want this marriage anymore.
I want this relationship to end.
I want to live apart.
Pick your own (things that can't be argued with, no criticism of him, make it all about you). And repeat them in your head.
Visualise yourself resisting that habit of defending your decision. He is not your boss. He can't tear up your resignation!!! This is a decision that you can make on your own.
What he thinks of you is none of your business from now on. You don't need to waste your energy trying to make him understand.
+
apologies if I've gone overboard here, but this is the way I wish I'd handled it. I only learnt how to deal with my x after I left him. I know now though! and luckily I don't give a fuck what he thinks of me. He can think I am Satan Katona if he likes. dont.care.
Now read it again, rinse and repeat!