Cat Update
We've been working with our two cats that don't get along for quite awhile now. Sagan has been leash trained. Each night we're letting Shadow out while Sagan is on his leash. At this point, I'm not letting Sagan follow Shadow downstairs or even fully approach him. I view it as allowing Shadow to call the shots since he's the one who gets chased.
Last night we had a significant breakthrough. We let Shadow out of the bedroom. Sagan was on his leash in the kitchen. Shadow came into the hall, saw Sagan, and started to hurry down the stairs. He then stopped a few steps down. Sagan moved to the railing and wanted to approach, but I didn't let him go on the stairs. Shadow stayed on the stairs a long time looking at Sagan. I let Sagan walk all around, but never go on the stairs. Often when Sagan felt resistance from the leash, he would lay down. Every time Sagan laid down, I praised him and gave him a treat. At one point, Shadow yawned. Then Shadow went the rest of the way downstairs.
Usually we put Sagan in his bedroom at this time, but he didn't want to go in there, so I let him walk around the kitchen with the leash on. After maybe five minutes, Shadow came back upstairs and looked in the kitchen. Sagan saw him, but didn't try to approach. He received a treat and praise for this. Shadow walked back down the hallway and went into the bedroom. A few minutes later, he walked back to the kitchen and actually walked past Sagan and me (I was sitting on the floor with Sagan) and went into the laundry room. Sagan got excited and tried to follow, but I only let him go a few steps. He then laid down. Treat and praise. Shadow then approached Sagan and they sniffed each other. No hissing or growling. Shadow then walked away and went back downstairs. John and I gave Sagan a lot of praise for not following.
This shows that Shadow has gained a lot of confidence around Sagan. In the past, Sagan didn't allow any time for normal interactions because he'd go from zero to sixty in two seconds. Shadow would always hiss and growl at Sagan, so it's a big deal he didn't this time. It must mean he didn't feel threatened.
Sagan seemed to enjoy the praise, especially at the end. I even gave him kisses. Maybe we've finally found a way to communicate to him what we want him to do (and not do).