I wouldn't look to the future Legs as being so fixed.
My children have left home, come back and left again, life is never a constant, there are twists and turns, not lonly for you but your children.
They know they can return, you being the responsible caring parent will mean so much to them as they make their way through life.
You are the stability and the backbone of your family, dependable and that is something he has not done, how could they respect that.
There is nothing trivial to making your home, the loveliest place to live in with as many comforts as possible. The dog idea I think as well would be a lovely addition to your new family dynamic.
Do you think the children would like one, would there be any help with it?
They are an enormous comfort, a talking point and an excellent replacement for men, well in my opinion 
You are doing well Legs, that well people mention you on other threads as an inspiration, you have been through so much and are coming out the other side.
Believe me, many of us on here are not doing anything more exiting than you, nobody is, we are just muddling along with our little distactions that bring us joy.
As times goes on those joys will increase for you and you may find your appreciation for things will return when you arn't even noticing it.
Take care x