damasa--
Have you thought about a reorganization? We did this with one of our floundering chapters, and it's done wonders for them. Basically, we said, ok, if you don't want to be an active member of the chapter, you're free to go early alumni. Those folks were sent off as alums, and then the rest of the chapter really got down to business. Sometimes, national organizations will do it for you, but if they come in, they may get rid of people who want to remain active, and it turns out ugly sometimes.
In any case, remember, that if you're in a national organization, you belong to a much greater organization than just your chapter. You belong to a national fraternity with numerous chapters. You obviously believe in the ideals and values and traditions of that fraternity. By staying active and getting rid of your dead weight, you can turn your chapter into a thriving group again. And you'll afford future college men the opportunity to experience your fraternity in the future.
I know, it sounds idealistic, but it really is the truth
*stepping off soapbox*