MrsHD are you sure he's properly hungry, or just he just like to suck himself off to sleep?
He sounds just like my DS2, who's 10 wks - awake for hours at a time, constantly appearing to want to feed but not always taking much. Miseralbe all the time, couldn't put him down
When he was about 8 wks, we decided to try something else as what we were doing didn't seem to make anyone happy.
I decided not to feed him any less than 3 hours apart. ( he was older than yours though, maybe go for 2 hours) I'll probably get flamed for this, but I felt he wasn't really hungry, just that I was misreading his signals. So when he started rooting, chewing his hands and chuntering after about 1 1/2 hours (when I'd normally have tried to feed him)I plugged the dummy in and went for a walk in the buggy. He immediately fell asleep, and woke up after another hour and a half, bringing us nicely to 3 hours. He then fed really well.
Dh took him out in the afternoon to stretch him out again, and once again he fell asleep immediately.
I realised he likes to suck himself to sleep and I was confusing his sleepy signs for hunger.
At home, swaddling him has hugely helped him drop off to sleep - I can't take him out in the buggy every time as I have DS1 to think of too, and it's been so darn cold! If I time it right, I can swaddle him, pop the dummy in and plonk him in the cot after a quick cuddle and he's off to sleep on his own - hurray! The dunmmy is key though, he likes to suck to sleep - but I've noticed he's getting less reliant on it already.
Some of this may be worth a try for you, though I understand he's very young still, so not worth forcing the issue.
HTH