First of all, I think that you may have recourse and remedy. I would get all your paper work together, all your realitors comments, and any paper work that you have pertaining to the sale and especialy the crawlspace.
Then I would seek out a lawyer if possible or if you want to test the waters go to a legal aid service. They will in most cases check this out for little or no money and tell you where you stand.
I think you were deceived, and the bias of the realitors father checking out the under neath and it being fine is there a possible misrepresentation of the truth and his position as a contractor.
I feel that with time and persistance you can receive your money back and win judgement against these people. You were lied to. You were deceived by the realitors father. His reputation could be at stake. find the previous intended buyer and ask him/her to assist you on this matter and ask them if they knew that there was water damage and how they knew.
Stand your ground and be a hard ass, you can win this injustice.