Well, don't think there is a magic solution, but willing to share my recent nightmare!! DC4 is 5 months and has been the WORST sleeper, day and night, known to mankind. Hence my FINAL beloved baby..
He has, from birth, catnapped for 10 minute bursts and has been tetchy and crying in between. Yes, it is utterly exhausting, mentally and physically: I have 3 other DCs at home, as we HE. This has been testing my sanity to say the least.
I always cosleep: have done with all 4: this helps greatly at night as shoving tit in mouth is preferable to fannying about picking them up etc. As far as life chez Catbus goes, the cot is rammed up against our bed from day one, mainly to act as a bedrail. 
Any road, last week I took nightmare boy to our homeopath: whether you credit homeopathy or not, the true test has to be with a baby. After the first remedy, he was even worse: crying in discomfort blah fecking blah, my hair falling out, literally and unable to cope for much longer etc. After 2 days, he has morphed into a calmer, smiley, chilled little fella.
Yes, he still cries; he's a baby: but he SLEEEEEEEEPS!!! and wakes happy.
Not all homeopaths will cut the mustard: mine happens to be a bllody miracle worker: I had the same problem with DC2: who slept 2 out of 24 hours for the first 3 months of her life, until sorted by same woman.
The difference this has made to our lives cannot be expressed!!
I do use a dummy, when comfort sucking gets annoying:as we cosleep, it's not hard to shove it in again: I would rather this than a thumb, which you can't remove eventually!
I so feel your pain though. I am just coming out of the fog that is sheer exhaustion and frustration and feeling vaguely human again.
I tend to keep DC4 downstairs with us, in the pram, til I go up: to be honest, I don't give a shit where he sleeps as long as he DOES sleep. All of mine have been ok to whack into a cot by 8 months, mainly as they seem to show me that's what they want..don't ask me?!
Apologies for disjointed post: brain will never be the same again. 