Braveheart is right. We can rant and rave about what our ex's are doing but it only hurt us and the one's around us. Especially your son. When one stays angry about whether the ex-spouse is being a good parent or not, one's energy is not spent being what one needs to be. If I am ranting and raving about my ex not being a good father, I am not setting a good example for my kids, and I am constantly reminding them of the hurt they already feel. I think that is selfish of me and I won't do it. What am I proving if I am always pointing a finger at my ex. Nothing except that I am an angry bitter person.
Your son deserves one good parent in all of this. Don't let her actions take away from what YOU should do as a parent. If you continue this way your son loses both of you. Don't let her actions dictate who you are.