A house contract of sale is like any other contract: it is legally enforceable. If one party to the contract (like the seller) breaches his legal obligations in the contract (such as by missing the contractually agreed upon closing date) the other party can sue him for "breach of contract" for any losses or costs they suffered due to the breach, such as increased mortgage costs, money spent on an inspection, etc. for a home which you could not end up getting due to seller breach, etc. Based on what you describe, you would appear to have grounds for a lawsuit if his delays and violation of the closing date causes you losses.