Still working at this. There have been signs of progress in that the cats eat near each other without incident. When they are together for short amounts of time, they are fine. When they are together in their "cat wing" of our basement they are fine. But when left together in run of the house after a couple hours the little bully just can't take it anymore and starts stalking and being aggressive. Using all the above stated products. Trying to keep them being positive for as long as possible then splitting up in adjacent rooms when signs of aggression.

You're doing the right thing -- even when cats are the best of friends, aggression can raise its nasty head. It's just something multiple cat households have to deal with. Just as siblings tend to fight with each other (and get along most of the time), it's the same with cats.

When Bengals grow up into adults, there can be some friction as each tries to exert their influence on the other and there may be fighting for territory.
I find cats who are equal in status have more problems than those where there is a natural leader and a natural follower. Though a highly territorial cat can start bullying a weaker one too.
I think the basement incident, catapulted both into reassessing their status in the household, and so now you have ongoing issues.
I guess the day that the younger one had the run of the house, left him with the feeling the house was HIS territory and the other one is now the interloper into HIS space. He probably thought the older one had naturally gone to find pastures new as they would do in the wild.
I think I would try and allow them to have separate territories, so that they do not have to meet too often, duplicate the food and the litter trays and place them in each "territory". Introduce some vertical space or more vertical space if you already have some. Cats are territorial, Bengals I believe are often very territorial and I guess with or without the basement incident you could possibly be facing the same issue.
On a better note, I had this problem at around the same age with two males who grew up together but suddenly there was serious fighting. Rolling on the floor, fur everywhere stuff, they couldn't stand each other and I separated them, never let them meet unattended. But years later they calmed down and became best buddies again.
The other strategy that I have heard of, is to lock them both in a small space with separate places to hide and leave them to it for a few days/weeks, they will sort themselves out, but that could result in injury I guess.

Elaine, it's good to see you back posting! I think putting both into a small space and letting them duke it out is not doing to work. Once there is aggression, it can be horrific unless someone is there to intervene! The b/w outdoor kitty I'm feeding has scabs on his neck from where Raiden got out of the house and attacked him. I was there within 5 seconds to pull Raiden off. There is usually a pecking order when it comes to cats. I agree that separate territories may help, but cats really need to get used to each other and they need to get along for the most part. Nobody wants to spend their lives separating cats. I think Elaine is spot on with duplicating the litter box, cat tree, etc. so each cat has their own stuff. Just like children, some cats don't like sharing.

I'm having enough problems dealing with a neighbor's cat who wants to stay at my house. I'm feeding it, providing it with a heated cat house for the winter. Long Legs is here a lot, especially when I walk Raiden and I have a hard time controlling Raiden on the leash. He wants at the cat and has run out the door and attacked him and they both ran away back in the woods. Thankfully, Raiden returned home a couple minutes later. Raiden would never accept another cat no matter what, so I do my best to keep these two apart -- even going out a different door if Legs is taking a nap in the cat house. Doesn't really matter as Raiden seems to sense he is there and we are walking around to the back of our house. There is no duking it out for these two. Raiden did a full-on attack and Legs has the scabs to prove it!