I hear you, OP. Four hours for me last night, with two wake-ups in that night time. (This is why I hate it when people say they had "no sleep last night". Really? Do you mean none at all? I definitely had four hours and that is bad enough.)
However, my baby is younger than yours so you're definitely feeling worse than me. Also, if it helps, on the second baby it seems easier to cope with the lack of sleep, even though I HAVE to get up with the toddler (who no longer naps). I feel tired, so very, very tired, but no longer like I might die.
Co-sleeping has helped exponentially, so I don't physically have to get up until he starts wriggling around needing a poo from 4ish. EVERY MORNING. Then he's awake for an hour or two, cooing happily, until he goes back to sleep at 6 and the toddler wakes up.
Will your baby take a bottle of expressed milk? Just so you COULD ask your husband to get up? Mine never did manage to take a bottle so I felt incredibly trapped, like I would never, ever have more than two or three hours' sleep in a row again, day or night, or ever recover. BUT! One night your baby will sleep through; you won't, you'll go in as normal every few hours to check they're still alive, but the next night you'll sleep and it only takes a few nights before you begin to forget the horror.
My PFB woke fairly predictably at 11, 2ish, 4ish and was up at 6, I recall. When she started snuffling at those times I would go in to her but just try to push her a bit longer, saying to myself I wouldn't feed her until 2.15, and the next night 2.30. Amazingly, this worked and she suddenly dropped the 2am feed. So then I did it for the next one and so on.
Good luck OP. You're definitely more tired and it's maddening. But he sounds like a keeper; don't let it come between you. Sorry for garbled, exhausted stream of consciousness.