Are these two cats from the same litter? There seems to have been a lot of things going on between these two cats before you even moved. Which brings up how were they introduced to one another? If one cat was already a resident of the house and another cat has been introduced without taking time to allow them to get acquainted properly over time, this can upset things for the resident cat. Cats being very territorial usually set up territories within the house that more or less suit them. And we as humans in a cats mind are fitted into this territorial system of theirs. They don't differentiate between cats and humans we're just all animals in their mind and the territories are somewhat flexible. Cats also have a tendency of rating their hierarchy status with the other animals in the territory or house. This is just a few of the things that could've come into play before you moved. As you said the move itself became a horrific stress factor for the cats. It's a wonder one of them didn't made a break for an open door to escape. Usually when they get put to the wall like this, it is either fight or flight and there was nothing to fight so the best thing that they could do is run from the stress factor. Or take it out on another member of the household, which appears to have been Daisy. Something else that didn't help matters is the new rental unit that you moved into. There's a good possibility that people who were in it before you, had animals and their scent would be all over the place. So it means establishing new territory over old animal scent from previous animals, and even today the basement is off-limits and maybe there is a scent coming out of the basement that is affecting them as well and without being able to get down there and investigate this could be causing the problem.
It's easy to theorize on this problem, but it appears is what you really need is some body in the know that can give you some professional help on the problem. It will take some time and a lot of TLC to work this out. I wish I could be more of a help, but I would appreciate knowing how things work out.