I have some advice due to experience. If you have a cash buyer, hold them to it!
We had a cash buyer and through the kindness of our heart, we let the cash buyer convert to a loan buyer. In the end it all worked out OK due to some excellent representation by counsel.
It was just a delay, but if I had to do it over again, I'd ask my attorney to hold the buyer to the contract on threat of contract breach if they try to do something else. I'm too nice. Remember, cash means fast and easy. This wasn't. My mistake was being nice.
Don't want to get into details, but this is what earnest money is for. Like I said, it was OK, but I did a lot of sweating. Our attorney really earned their pay, with multiple extra correspondences and closing calculations. The OP talked about nit-picks. We had those. I understand, because we had every possible flavor. It would have stopped real quick if we told counsel to "put the hammer down" right away. Counsel eventually did put the hammer down on my behalf. I love my lawyer today!
Maybe I haven't given up on real estate. I'll just take this as experience. It is too bad that in America (maybe the world), if you are nice, you get stomped on -- or at least they try to stomp on you. What has happened to decency in this world?