Hugs, sweetee...
It is one of the most difficult parts of my life, I find, to not try to compensate for the absent/sh*tty other parent. You can never replace their father -- but you can be honest about (as Buffalo said) how everyone has to make their own choices.
My youngest was a few years older than yours when we left -- but she was blaming herself, thinking that her father's drinking was her fault. If only she hadn't fought so much with her siblings; if only she would not laugh so loudly; if only... (just like I did during our marriage).
Dealing with the children's pain is hard, because you don't want them to suffer. But allowing them to express whatever they're feeling makes them more and more comfortable. And you've already got a fantastic start with that little one.