I say tell people the limited truth as listed below. Like "we are really taking a financial hit with all the gas prices and higher groceries. To stay on budget we are having to make some drastic changes. Although we can't eat out and things like that, we would love to have you over for game night instead of breaking our budget." Then bake some cookies or something, make smoothies, make coffeee, make a cake. Serve some veggies and ranch. It is great to play board games. Especially with your adult friends. I always think, now why aren't we doing more of that.
As for the birthday party. I would just say that our schedule didn't work out and we regrettfully can't join you. And technically, your schedule didn't work out, your schedule for money. Schedules are more than for time.
As for your hubby, men aren't just told by society they are the providers. It is an innate reflex to provide for and protect his family. Many men have self esteem issues, depression and anger over not being able to provide adequately for their families. It is part of who they are. Not just what society thinks, but how they are made and wired. God made them that way.
THere is a book called "The proper care and feeding of husbands" by Dr. L. Schlessinger. It talks about this feeling of providing for the family that leads some men to be workaholics among other things. It is a very good book. It might help you understand and cope with his feelings and help you to help him. It is geared towards wives wanting to better care for and tend to their husbands, on many levels.
I would also reinforce with your husband that providing for the family financially is great but it is not the only thing he contributes. That he is important for that and does a wonderful job. And he can't control the economy. But that he also provides a stable home environment, moral compass, presents a good example of a good work ethic, provides for your emotional well being, and your physical well-being (and he is a millionaire in that category--GIGGLE), is a great dad to the kids. This is also a good time to teach them how to handle adversity. Whether it will make you or break you...or your marriage. Remember the kids are watching that also, especially if they are older. Younger ones may only feel the tension.
You could also look at it this way. Now you guys can spend some more time together doing inexpensive but family bonding activities. Projects that you are always meaning to do but never have time, like pruning trees, weeding flower beds, planting seeds, go to the library, the park, nature walks, games in the evenings. I would also tell my husband that since we are no longer spending money for entertainment, then he will now be my entertainment and it starts right after the kids are in bed. That should reinforce that he still has something desirable that you want and admire him for.
Anyway, I think we are in this boat at some spot or another. I always tell my friends that I can't do something because it just isn't in my budget, and then substitute what is.
Good luck,
L.