He's really getting desperate, isn't he? Again, don't engage. Just either ignore or respond with a disinterested 'hmm' to anything he says. He's still trying to get a 'spark' of sympathy going in you so he can fan it into a forest fire. Don't let him.
I know it's hard, rather like someone continually poking you in the back in a queue. But you must let it roll off your back. Just repeat "Not my problem anymore" or "too little, too late" in your head.
I know you don't want a 'scene', but I do think you'll need to face him and tell him to leave at some point. His type isn't going to give up and leave of his own volition. Well, he may 'give up' but he won't leave. Why should he? He's not really feeling all the 'pain' he's carrying on about. He's perfectly content to let things go on like this forever. He has a roof over his head, a home for his children, and you to do the hard work of 'family life'. All he needs to do (in his mind) is carry on with his selfishness, interspersed with token gestures of 'kindness' and random displays of sorrow and/or guilt. Think about it, exactly how 'uncomfortable' do you really think he is with the status quo? My guess is 'not very'.
I know you aren't ready today, not even tomorrow. And that's OK. But I think you should set yourself a mental timetable for, perhaps, sometime soon after the holidays? No one wants to deal with something like this during the holidays plus it'll give you time to really gird your emotional loins for 'battle', confirm all your finances, perhaps start saving some money for deposits, and set a definite plan for a place to live (check rentals in your area so you'll have an idea, etc) in case he refuses to leave. And it may actually make the holidays easier to get through if you have a date in your mind: "On 10 January I'm telling him to get out by 30 January. I only have to put up with this until 30 January". Then you set your own plans for 1 February. Whether it ends up with you gone or him gone, at least it's done. (I'm not saying 10 Jan or 1 Feb, those are just random dates)
Remember that if there's going to be a 'scene', there will be a 'scene' whether it's tomorrow or 3 months from tomorrow. I hate scenes too, with a purple passion. They make me ill, figuratively and literally. But I've found that postponing them never makes them 'easier' and the horrible sick feeling of anticipation I get usually just makes the scene worse, because I've expended so much of my emotional 'strength' in dealing with the anticipation.