Buyer threatening to force sale of house!!

On 4/5/00 I entered into an offer to purchase and had to entered into a P&S by 4/16/00 (I am the seller) later that same day my septic system failed title V. I immediately informed my realtor of this. On April 7 I was given a P&S to sign (already been signed by buyer). At the advise of my attorney I was told not to sign P&S because of septic too many liabilities. On April 14th I advised my realtor of this (I would not sign P&S at advice of my attorney). On April 20 I received a telephone call from the realtor found some septic langauge. Again advised him language doesn't protect me will not sign P&S. I proposed that the buyers fix the septic and we will lower the already agreed sale price of the home. On April 24th I was advised by the realtor that the buyers declined. So on April 24 I put realtor and buyer on notice that all agreements were hereby terminated pursuant to the septic system clause. I also advised the realtor verbally that the deal was over. On April 27 I received a call from another realtor asking me of my intentions, what if we did this, proposed that, buyers don't have $ to fix system . . . she was more than a "pushy car salesman". (Since April 14th I feel as though I am being pushed and cohersed into doing something that I really don't want to do and it makes me uncomfortable. Anyway this realtor said she was have the paperwork drawn to end everything. On April 28 I received yet another call from the realtor, new developments the buyers found a bank that allow them to fix the septic, what are are intentions. On April 29 I advised the realtor that as far as I was concerned this dealing was terminated on April 24 and should have been terminated on the 14th when I first advised that we will not be signing a P&S Agreement. On April 29 I was finally allowed to sign a release to release all deposits to buyer. Now I found out that the Buyer refuses to execute this release and is seeking counsel to force us to sell the home to them. Can he do this???? Does he have a leg to stand on????