Realtors are not attorneys, nor can we offer any legal advice; the following comments are not intended to replace the advice of a competent lawyer.
Emotions often get in the way of accomplishing the end goal of selling a home. What you might want to consider is having your "tenant" voluntarily leave your home in advance of the settlement by offering to put them up in a hotel for an agreed period of time and storing their belongings, if required, for a specified period of time.
Before doing this, contact your Realtor and ask them to contact the buyers' agent to determine if the contract can be resurrected and the deal put back on the tracks. If so, have the tenant vacate immediately, commit to a settlement date and then get on with life. It sure beats having to pay commissions and legal fees, while still having a home to sell.
Best of luck to you.