New Home Construction - Bad Builder

[James Brueggeman]

Hi All - looking for advice here:  We are building a new home (a very nice one btw - $550k+).  We started the build last November and structured it as a turn-key property where we signed an offer to purchase with our builder.  We fell in the love with the property and it was build to suit so we didn't have a choice but to go with this builder.  Anyway, we are about two weeks from move in and our offer to purchase expired on April 30th.  In the meantime, our builder just hit us with almost 40k in overages and has been completely unresponsive throughout the process.  We have over $20,000 worth of insulation, fixtures, appliances, and other miscellaneous items already purchased and in the house along with a $37,000 down-payment.  My question is how to proceed with no purchase agreement currently in place.  What are my options?  Can I draft a new offer to purchase at a lower price than the numbers he just gave me?  Any advice is appreciated as this is new territory for me.  Thanks!