I didn't have twins, but a lot what you feel resonates with how I felt with PND. Including your other post about ruining your DS's life, I posted something very similar around the same time (a week or so in).
I found it so difficult to admit anything was wrong that I had to write it down for my husband to read. Like you I am known for being 'able', I work for myself and lots of people comment on how I fit it all in etc. So I too felt I should be able to deal with this.
I went to the GP and went on a low dose of anti-ds. Was the best thing I could have done. I wasn't jumping for joy when they kicked in but I felt I could cope, which I didn't feel at all prior to that. I took them for about a year and I feel back to myself now, DD is 2. If it is PND, take the tablets. I was really reluctant but I am so glad I did.
I also think you have to muster up everything inside to tell people what help you need. I could imagine how I would have felt in your shoes if my DH had just decided to nip off to bed leaving me with the 2 babies. I think I might have felt invisible/upset/overwhelmed. You need to say something, he needs to know that he cannot just do that.
Can you go to bed at 9 and he does the first feed, so at least you get a small stretch of sleep?
If you decide to move to ff, try to forgive yourself. I never got on with bf and it took a lot of feel ok with bottles. You have such a lot to gain (help from whoever is about) by moving to bottles. Your needs are just as important as the babies.
And try to remember, that in 6 months no-one apart from health professionals due to records) will even know how they were fed.
And try to find some twin mummy friends, they will understand like others probably cannot.
Try not to worry about DS. He is gaining 2 siblings which will provide him with fun and laugher when they are old enough. I have 5 years between mine and they really do love each other.
Big hugs. It will get better. Keep posting.