Oh Littlehappy, please try not to let his actions define you.
I know this is easier said than done, I've been where you are and you feel helpless, mugged off, and utter sadness.
You are better than this, he might look like the life and soul, and you might look like the bore (to his so called friends) but you are not and neither is he! He's not the person you once knew, he'll gravitate to like minded drinkers or coke users, it doesnt matter that before he'd never socialise with them, now he'll socialise with anyone who is on his level, a messed up level, a level that you never want to be at.
When my husband used to be like this, I researched cocaine psychosis, and I truly believe my husband had that. He looked at me with hatred, the drug hated me for trying to help him, and he was now that drug, it had consumed him, and turned him into someone I did not recognise. I saw photos on my phone the other day of him at our childs graduation from nursery school, and the angst on his face is clear to see. He wanted to be there, but he didnt want to be there, he was so messed up.
Never, ever, blame yourself. Nothing you have done has made him like this. He's an adult and you can't fix him, so you need to look after yourself, and your girls and do whatever you need to to start again, find happiness and start to LIVE again, instead of the existence you have at present.
Sending much love x