In terms of lawyers if the rebate/price cut doesn't work. Then a legal firm like this appears to be in the business of what you need. Their whole website is more focused on this type of situation. I've never used them, but it came up in a quick search. Before I signed on a firm like this I would would want some references as to how they operate.
Lol...I don't use the term abatement for the price cut as that term is many times used in the description of a mold treatment (mold abatement).
http://www.gilbertsondavis.com/real-est ... e-dispute/
They do have some discussion of latent defects on the site that might be of interest.