Just reading your story speaks volumes about how dedicated to those kids you are mate.
Money comes and goes but that love you have for those kids is forever pal.
I understand times are hard, I don’t think you should let her treat you like this with seeing the kids. You need to get some legality down on paper for a set routine for yours and their sake.
Someone will appreciate you for who you are mate so keep your head up.
If you ever need to talk I’m always a willing ear to listen.
No one should tell you how you should feel. I’ve personally gone through similar circumstances and there is a stigma around men talking, but it honestly helps. I found talking to my doctor helped a hell of a lot and they can offer further guidance.