Yaay! Your fish are going to be so happy! Not your wallet though. I think so far I've spent at least... what... $300-400 on one fish? Not sure, I've lost count. I haven't really read into the Red Loss Factor thing, so I can't say. Them flaring at each other is good, it will be their "exercise" but if they do it TOO much (more than they are now, as in like almost always
at the divider or something) then yeah, maybe we'll need to go back to separate tanks again. It will give them a lot of stress if they do it too much like you said, yes, but so long as they're not at it for really long or really constantly I think it's OK. Don't worry about it for now, I don't think you have an issue with it.
Did you make Nick make it by himself? haha, yes, from what I hear they are quite hard to put together (at least a good strong one!). I'm glad to hear that it's not too flimsy, but if I were you I'd still watch it like a hawk. People have had issues with seemingly functional dividers before, and ended up losing a fish as a result.
Sometimes they do work, but then they get bendy, fish attack them and wear them down, etc, depends on what you used to make it. Be very careful about this, don't judge a divider by its cover!
If in case one of them gets over to the side of the other's, you'll want to remove one (Akumu will be most likely to attack) ASAP via cup and probably keep him in the 1.5g until you fix the divider. This is the worst-case scenario, I hope I'm not scaring you or anything but I always think it's good to be prepared.
Overall it sounds like you have a good plan going on there! And you don't have to write out JewelQueen, it's a pain in the butt to type. I'm just plain old Jewel.