I read early on in my parenting journey that the more you have the more often you should say no to your kids. It has really helped. My girls are teens how and will hug and kiss me and send cute texts thanking me when I get them something at the grocery store they wanted.

It is good you are including your son in helping others. After Covid you could expose him to kids that are in need that he may relate and feel more empathy for. Regularly doing community service with kids in key. Until Covid we helped host a monthly free meal for the community. Since we have some deaf regular guests my girls took it upon themselves to learn the opening welcome message in sign language. Once they contribute like that it also helps their self-esteem and they become more generous. Don't give up. (But maybe save some of your money and stop buying so much Jan-Sept)