a few things i have in mind,
1) can you tell us who is the lawyer you hired, have to ban them for life.
2) since they did not pay up during the agreed time frame, by right you can forfeit the deposits. I think you can inform the other party's lawyer that you will take back the property and put your property back on sale.

i have learnt it the hard way that you should never allow the buyer to move in without receiving full payment for your property, always resist the temptation no matter what they offer you.