When I had a spraying male several years ago, I read somewhere that since cats will supposedly not "pee where they eat" that putting a bowl of food in the spot could deter them. This person I read about had food bowls all over the house, but it eventually worked. (I can't exactly say it worked for me, but I had tiny kids and not the time or wherewithal to be vigilant)
You could try it - particularly for that problem spot by the door. (When I've had peeing cats, they've always chosen the front door, too. WHY?????
I just realized something... you said squatting. That doesn't usually indicate behavioral, as spraying does. That usually indicates a medical issue.