hi, i can't really say anything about not being invited to the graduation. 1st, if they didn't invite you, it means that his daughter doesn't want you there (as you said, she thinks you're a "home wrecker"!) why would you want to be around people who don't want you there. 2nd, it most likely would be very uncomfortable to be around his ex wife and her family (which i would assume would be there). just don't let it get to you, think about it as, "hey, that's one less moment you have to play nice with people you just don't get along with", even if it's on their part that you're not getting along.
as for the support. from what i know about the law and child support....a parent that pays support is required to pay until the child is 18 OR out of school! (unless of course there's some other circumstances like a disabled child that will probably always be taken care of and living at home...in that case, i have no clue on the laws). since she is not only 21, but also JUST graduated...the support should be DONE WITH! as for him paying her cell bill, and giving an allowance (i always thought that an allowance should be given to a child when they do something to EARN that money, not just handing the money out, that's the way you raise children to not know the value of a dollar, and to have them not want to work, or support themselves because they can just go to daddy or mommy for money...just wrong on his part if he's just GIVING her that money!) handing her money is definitely HIS CHOICE! whether or not it's the right decision, or the right reasons for giving her the money, that's his decision, he's working for it, he can just hand it over. BUT i just have to make one suggestion, whether it starts a fight or not, the next time he complains about how he has to work so much and see so little...make it a point to say something about him giving her the money, and paying her cell bill. tell him something like "you work hard and see nothing for all the work, just look at your daughter while she's talking on her cell...YOU paid for that...happy now???" or how she can go here, or there, and do what she wants because he hands her money...it MAY start a fight, but it's the truth. like another person said, you should write down all the money he gives her and the reason he gave it to her (pay a bill, buy something, go somewhere, etc.) and then show it to him. maybe he'll realize how much money he could save if he didn't just give her this money. MAYBE he'll even tell her to get a job now that she's graduated and out of school, and have her start supporting herself. BUT you have to realize that if he stops giving her money and paying for things, that it will most likely get back to her (and her mother as well) that YOU were the one that got her father to stop paying money, and i'm sure it's safe to say that any negative feelings she has for you WON'T get any better, they will just get worse! most likely you will no longer be disliked by her, and will then be just HATED.
just to make one thing clear, i am in no way saying that you are wrong, i actually think that you are right about the money thing (especially since she's 21 and out of school) but you have to realize that if she feels you are a home wrecker, she's holding YOU accountable for her parents not being together whether you were with him when things were over, but not finished with his ex, or you waited until the divorce was final...either way, she blames you, and you can't change how she feels, you can only attempt to bridge that gap you have. try to invite her for lunch, or dinner, a movie, anything...but if she refuses to try to work it out, then let her be bitter. just try, and if it doesn't work, don't push it. she will feel how she wants, and maybe sometime down the line she will lighten up (just don't hold your breathe...people can be stubborn!). good luck.