Great post OP!. Its good to see someone with the stones to confront people.
The husbands anger is driven by the fact that his long con has been ruined.
Part of being an adult with different kinds of friends is understanding different peoples circumstances. Some people are just oblivious and don't think before they make offers. You might risk offense by exclusion, but you also risk offense by offering something that you should know the person cannot afford to do. My good friend is a divorced friend with 5 children can't do what my other friend with a "time piece" buying habit can do. I know this and account for it BEFORE I try and make plans.
Some people are so cheap that they don't care if they are others turned off by the habits or lack lack of social graces they exhibit.
As for friends and favors, to me that is a personal issue. I'll be honest, I am keeping track. "Can I get a ride to the airport?" is really asking for 1-3 hours of my time depending time of day and 1/4 of a tank of gas. The private airport service is $45. The light rail is $3 but takes 4X as long with no traffic. So if I give you a ride to the airport, I want a ride in exchange. I will often check on my friends cat when they are away and get some Chinese food in return. Its a good deal. :) I have a friend who will help anyone anytime, yet he will never ask for anything, so I never ask him for anything.
And my Mom taught me to never go to someones house with cake!!!