What a difference a month makes......!
This mommy is no longer stressed. As it turns out, coupled with the depression from BIL's death, it seems that when Bucky was being released from quarantine, I was coming down with a case of the shingles, as well. Now I understand a little more why I felt so 'stressed'....
Anyhow, a Christmas visit from the family also provided a well needed 'break' for Bucky and Lotto. My family was able to provide some additional entertainment for Bucky (and vice versa), and Lotto was able to get some peace and quiet time to himself. My assessment now is just that it takes Lotto a very long time to trust another cat/kitten, and that until that happens, he is just unable to be distracted by much. But resting went a long way toward his coming back to his old self.
Gradually, he and Bucky have gone from mostly fighting to mostly playing with small tiffs about every 3 days or so. Currently, Lotto is coming out as the alpha, as Bucky wants to play with him so badly that he is 'learning' how to back off. I'm not sure how long that will last, though, as at 5 1/2 months, Bucky was already 10 1/2 lbs! Tootie and Bucky have also made progress, as Bucky has realized that if he doesn't attack Tootie, she will occasionally play with him or let him sit on the window sill next to her to watch the rabbits and birds. It's amazing what a motivator play and companionship is.
Bucky, although not a very affectionate kitty in the conventional sense, has been showing his affection in his own ways. When I get home from an outing, he will purr and stand up to bump my hand....and he will often come get right in our faces and sniff and purr at random times throughout the day. He is still definitely the jock, and likes to play more than anything. But he wants to be involved in everything that we do and now usually sleeps with us in bed, as well.
Lotto and Bucky still have some things to work out - for instance, Bucky wants/likes to sleep with Lotto, and Lotto doesn't particularly care to have Bucky sleeping with him at this time. So occasionally, when Lotto is REALLY tired, they will have a few minutes of sleep time....but then Lotto will wake up a little, growl, and move away. And they also have to work out who will be sleeping where in the bed, as Lotto doesn't seem too keen on sharing his space behind my legs. But in the grand scheme of things, these are minor issues which they will eventually figure out on their own.
Peace has returned to the household (most of the time), and everyone seems a little bit more relaxed and used to the 'pattern' of things.
Thank you for all the advice, and sorry to bother everyone with what are probably the usual introductory woes. Apparently I just had too much going on at once, and with a concurrent illness, was not up to my usual standard!