My son's father gets on my nerves

My son is 16. He's also a teen father. My grandson is 2 and both of them live with me. They go with my ex every other weekend and he is such an ass. First off he doesn't understand why I don't allow him to claim either our son or our grandson on his taxes. He thinks it's only fair since there are two of them. Maybe because I financially support the both of them. He didn't have a bed or a crib at his house for either of them so I paid for it. This is his Holiday with our son so they both went to spend the 4th of July with him. He told me he didn't have food at his house so I purchased a little food to last them the few days. He was furious at me and said that why wouldn't I fill his fridge. Why would I? He told me he knows I get almost $500 worth of food stamps and there is no reason I shouldn't fill up his fridge. Especially since he's going to a bbq and can't go empty handed. I said no. I got enough food for them all to eat. Those food stamps is for food at my home. He asked if our son could pitch in since he works. I said no. Me and my son's deal is he saves 60% of his money and can do whatever he wants with the other 40%. That is his money. My son and grandson came back yesterday and said he can't wrap around his head how selfish I am. I get food stamps. I get to claim the kids on my taxe. How can I be so selfish and not give him anything. I told him I'm just so happy that our son is a better father than him. Maybe that was a low blow but I'm so over him.