My boyfriend/baby daddy is addicted to kratom/7oh

I’m really at a loss of what to do. We have been together for a long time and have 2 kids (2 years and 5 months). I started noticing him nodding off a lot and acting weird a few months ago but he’s always been a heavy marijuana user so I thought he was just overdoing it. About 2 months ago I confronted him after a few particularly concerning situations and he confessed he started taking kratom and then 7oh and it spiraled quickly and he couldn’t stop. He’s lost basically all his money and I was only working part time due to the baby so financially things were not great. He said he needed a few days to detox but he was glad that I brought it up. Things got better after that.Fast forward to a couple weeks ago and he was gone basically all day and came home acting so strange. I know I shouldve intervened but he said he was going to take our 2 year old outside to play on the trampoline and when I came out of our bedroom, he was standing there and had left our son outside by himself. I brought him in to take a bath and my partner said he’d watch the baby while I gave the 2 year old a bath. About 10 mins later I hear the baby crying and I went out to find him all alone and my partner had passed out standing up in our bedroom. I kicked him out after that and he’s been living with his mom. He can now only have the kids if another adult is there. I told him that I’m willing to work on things but he has to be sober and he just can’t do it I guess. This morning was a breaking point for me, I had to enroll the kids in daycare so I can work full time since he still doesn’t have a job and is providing no financial help. Today was their first day and my partner wanted to come with us to drop them off, but I could tell he was high and couldn’t even make it through the drop off without taking something. My 2 year old is really struggling because he doesn’t understand why his daddy who used to spend every spare second with him is no longer around and I’m afraid the baby will never know what it’s like to have that dad. I feel like I should reach out to his mom and try and discuss it with her but she tends to be a bit of a “boy mom” and I’m not sure if it will go well. Any advice?