How to get baby to sleep in bedside bassinet

Since my baby turned 3 months he has refused to sleep in his bassinet. He used to be able to sleep for 30 mins to an hour at a time in the bassinet before waking up but lately he will wake up and scream as soon as his back hits the mattress and won’t settle until I pick him up again.

Because of this, I have been chest sleeping with him and this seems to be the only way to get him to sleep for a long period of time. The issue is that my bed isn’t safe for cosleeping. The mattress I have is too soft and caves in when I lay down on it and I share the bed with my baby’s father who vapes. The bed is also very high so if he rolled off that would be an emergency. We wears the owlet sock at night but I don’t want to rely on that to keep him safe. We also don’t have the funds to buy a new mattress and there’s no where else for me and baby to sleep. I make it as safe as possible by propping myself up at an angle, sleeping shirtless, having my bf sleep on the couch, etc but I know it’s not enough.

I put on white noise every night. The room is very dark. My baby won’t take pacifiers. I’ve tried putting the mattress sheet in my shirt so it smells like me. I’ve tried waiting til he’s in deep sleep to put him down but he wakes up within a minute. When I lay him down I practically have my whole body on top of him in hopes he won’t notice he’s not on me anymore but that doesn’t work.

If anyone has advice to help train my baby to sleep in his bassinet again please let me know.