I'm sorry you are going through this. We also struggled with this with our child. She was two when she finally started sleeping well. I read heaps of books. I read heaps of blogs, internet info etc. I listened to doctors, nurses, friends, family. I blamed myself for not getting the routine 'right' from the beginning. Why didn't I read babywise sooner? I blamed my husband for not following the latest idea I had. I was miserable, and so was the baby. I resented becoming a parent.
Based on what I had read, or what others suggested, I would change things frequently to try to get some sleep. Eat/play/sleep, play/eat/sleep, wait so many minutes before going in, earplugs, driving around in car, walking around with stroller, carrying around in carrier (slept well but sore back and hard to do anything like wipe own bum, also can't use at night), side cosleeper, cot in same room, cot in other room, white noise, no noise, loud noise, dark room, light room, looking for sleepy signs, putting down drowsy but awake, putting down awake, putting down asleep, outside, inside, in bouncer, 2 hour cycle, 3 hour cycle, 4 hour cycle, breastfeed, pump and bottle feed etc etc etc.
Now that I am not in the sleepless thick of it, I have come to the conclusion that her (lack of) sleep behaviour was normal for her age. Some babies sleep well and others don't. It was nothing that I did, or didn't do, or read that made the difference. Nothing at all made a real difference, except the carrier and then only during the day. It was just her. And I have relieved myself of the burden of responsibility for that awful period.
If I did it again I would spend more money, get more help, take the night in shifts with husband (as I see someone else did above), drink more wine, and just try to go with the flow. The house would be messy, the washing done infrequently, microwave meals, sleep when baby sleeps. A lot of the stress was from me worrying I was doing it wrongly, and the lack of help. It may have been easier if I had just accepted it. Also, getting more scheduled time away from the baby would have been helpful too. Somebody to take the baby out of the house every day while I slept would have been ideal.
Going back to work was a huge relief for me, even despite the poor night sleeping.
As for the recommendation for a dockatot, they aren't recommended for safe sleep. They aren't marketed as a device for sleeping in. And safety should be first in my opinion, no matter how desparate you think you are.
Also I have a friend who had a baby that slept well at the time. That made it worse. She would say it was her strict routine that made the baby sleep well. She has since had a another baby who doesn't sleep, and now has some insight into how I felt.
Tldr: No device or change in what you are doing will help. Your baby is normal. Do whatever you need to for your own mental health.