I could have written your post, hang in there, you CAN do this. It was hard but we managed it despite being at a starting point of me going to bed with ds at 7, feeding to sleep and staying with him all night. Does he feed in the night?
I started by getting him to unlatch whilst still barely awake, the Pantley pull off if you've read the no cry sleep solution? It was a slow process, took a few week but we got there. I was very anti cry but soon realized that for us there was going to be some crying but never left alone at the start.
I got help from a USA company which is email based but very very helpful and supportive. I'll let you know who if you want to pm me, not sure i am allowed to post the name. The key was getting ds to fall asleep in his cot, by himself at bedtime. I thought it would never happen.
I started with bedtime only, carrying on feeding to sleep at night wakings which were 2 hourly til he was 10 months. I let him fall asleep on my bed without boob in mouth, I unlatched him nearly asleep & if he complained I let him relatch for a few mins then tried again, repeat and repeat until it works. I think I did it for an hour one night. Once asleep I stayed with him for 20 mins until in deep sleep & crept away. Gradually I could unlatch him awake but sleepy and then cuddle/sshh to sleep. It took a few weeks. Once that was achieved I settled him on my bed & lifted him into cot awake but sleepy. I stroked his back & sshh'd to sleep, it was hard, took ages in the first week but then he got the hang of it himself. It was still only at bedtime though, we co slept after his first wake up & fed to sleep.
Once we mastered that, I decided no milk or co sleeping til midnight, just resettling by sshh and stroke, never taking out of cot unless absolutely necessary. I extended that to no milk/ co sleeping til 4, then 6.
I still fed to sleep/co slept at naps as without good naps night sleep was truly awful.
Typing this it sounds quick and easy. It bloody wasn't. We tried PUPD, CC, didn't work for us, ds just got the rage. I did have to step away for 5 mins most nights at bedtime to compose myself, ds howled but calmed down too.
I wouldn't try sorting night & naps together. Nights then naps worked for us. Not that nights were perfect before we started on naps, just better and so I felt more capable. I think my ds could still only manage 2.5 hrs awake before napping at 8 months. Over tiredness wrecks bedtimes & night sleep here.
Eventually we got to the point where I put him in his cot sleepy, with a musical nightlight and left the room. At first he cried/grumbled for 10-15 mins but that reduced to about 1 min over a few weeks.
It was awful but necessary. Once improvements started it seemed to get better in leaps with a few setbacks. Sleep deprivation is a shocker. Keep posting and good luck 