Hi ark - sorry you are having such a rough time.
Between the ages of 6-9 months me and DS co-slept pretty much every night and I was never worried about safety as he was under the quilt with me and I knew that if he woke up the first thing he would do is wake me up.
At 9-10 months old I carried out sleep training because I had 101 issues with his sleep and I couldn't physically and emotionally cope anymore. After sleep training my DS slept all night in his cot every night so co-sleeping was no longer an issue.
However, DS is 17 months now and over the last month he has been a nightmare with his sleep and he ends up in bed with me about 2-3 times a night. When he was in bed with me I couldn't switch off because I was too scared to fall asleep in case DS woke up, got into mischief and hurt himself. Whereas I used to be trust that he'd wake me if he woke up, I know that these days he would instead creep out of the end of the bed, lower himself to the floor and start doing Lord knows what. As a result I was barely having any sleep as like you, all I could do was doze. I'm a nurse to working long shifts (I'm out the house for 14 hours on the days I work) and I was having to go to work on about 4 hours broken sleep and I was just exhausted.
As a result, and much to DS's disgust, I have started putting him back in the Gro-Bags because it means that if he does wake up it makes it a hell of a lot harder for him to crawl/climb out the bed without it disturbing me because of how clumsy it makes him. I've also taken to tucking the bottom of his Gro-bag between my thighs so that if he does try and escape out the bed the minute he tries to crawl away from me his movement jolts my legs and so wakes me up.
It's not ideal and it doesn't remove all risk but it definitely makes me feel more reassured.