He’s not in his right mind at the moment so he wouldn’t even be thinking what it would be like if you weren’t there. As far as I know you can only really have a talk about it when they’re not on it and when they aren’t on a terrible come down. If you can catch him sober at all then you could explain what this is all doing to you and your family.
Maybe if you don’t feel comfortable yet telling them what’s going on you could word it that he hasn’t been feeling too well and see if they can help at all? If they were around or if they speak to him they might realise how bad it is. Yes I understand your concern of breaking their heart but I guess if you leave eventually they will find it all out anyway but it would be too late for them to help then.
Did u think of anything nice to do for yourself, you are worth treating yourself and hope that you can realise this.