In your world, right and wrong are evidently much more obvious than in mine. I'm not sure it's fair to bludgeon Will for not doing more for Father Tim and his guys, since his family has done quite a bit for that organization, and Will spent some time volunteering there (we really don't know how much since I didn't delineate his hours). I think he's pretty sensitive to the fate of those guys.
You have slotted Will's purchase of a car in for Zach as a charitable act (comparing it to the Mission) and that's really not where Will is at on this. He bought the car for Zach as a present, a gift, for a number of reasons. The primary two would be because he slept with Zach (and Will tends to let his dick lead his heart...and sometimes his head) and because he sees Zach struggling with his parents in a similar way to how he had to struggle with his. To him, he's helping out a friend, and righting an injustice as he sees it. That may very well be wrong, but I don't think the motives are evil. I can see how you can interpret that as a lack of maturity, since Will really didn't factor in Wally and Clara at all, but personally I don't think that's the best descriptor. I think it's sufficient to say that Will has a general lack of respect for Wally and Clara (see comments on that below).
I think this is a much better way to look at things, and I think that really is the unspoken issue at this point. There's definitely some socio-economic-education level issues going on here. Will is looking at Wally and Clara as if they're uneducated country bumpkins who don't have a clue about Zach and the world he's living in. Wally is a blue-collar garbage man who probably has a high school education. They're clearly not very sophisticated. I think you can certainly nail Will on being arrogant when it comes to them.
That's pretty funny, and pretty astute. Do remember, though, that how easy it is to fire people can vary by state. Regardless, we'll see how that drama unfolds.