Hold on!
I attempted suicide once, due to a flailing, dying relationship. I was as depressed as is possible to be, not one of the medical professionals thought I'd live.
Not ONCE did I blame my then H, or my rubbish, unsupportive family.
This bloke, for whatever reason, has gone off on one, drinking, harming, CHEATING ON HIS WIFE and DC, and then, instead of working toward inprovement has stalked off, moved out, and is carrying on with his life. But blaming the OP for the state of it.
So why call his friend? Ok it's a cry for help? Then GET help then! But don't BLAME the wife you say you are missing.
He's messing with everyone's mind. OP, protect yourself. When you get the opportunity, express to him that for him to do this to his family is the very worst abuse of his DC possible, that their lives would be blighted forever if he leaves them this way, that this is not the way it's going down, that he needs to get help, or you'll have to distance yourselves for your own protection.
I'd suspend unsupervised visits for a while too, the DC could be at risk. No-one's worth that, so until he's taking responsibility for his health, no unsupervised access. If the supervision proves hard to arrange, suspend the visits. Tell him why.
That should bring sharp reality back to him and incentivise him to sort himself out.