Most of the people I knew just sucked it up and lost the deposit. Myself, I had a deposit on a preconstruction out of state. I ended up changing my mind. Fortunately, the deposit was only like $500. I really have no one to blame, so I gladly forfeited the deposit.
Getting an attorney to fight over 20k is probably not worth the hassle/cost imho. To really win, you’ll probably need a good attorney. Good attorneys don’t come cheap.
You might want to get your in-laws to talk to pardee to see if they can make an exception. Provided they can quickly find another buyer, it might not be that bad. When I last spoke to Pardee, they claimed Carriage Run was sold out and there was a waiting list.