Update and the new things I've been trying lately:
Feliway diffuser is in place (and generally following Bean cat from room to room).
I've slowed down a bit on the visual interactions, usually keeping the door closed or open just a bit when I am in one room or the other.
I think Bean is nervous of the kitten noises, so I've tried to muffle the sound of him jumping on the door and climbing (it's like a folding closet door with slats on the upper half). It can get pretty loud and I think it makes him sound more intimidating than he really is.
I'm also exposing Bean to kitten's pheromones. He never rubs his face on anything, so last night, I took a clean sock and rubbed it on his cheeks. I feed Bean some treats right next to it and she was fine for the first few, but then it was like she caught a whiff. She didn't take the last treat and started to slink over to her cat cubby a few feet away. She stopped and turned back to look, but she wouldn't eat the treat until I moved it away from the sock. That was a surprise. I had assumed they would have smelled each other very well by now, but I guess since he doesn't rub... that or the sock wasn't as clean as I thought.
So kitten sock will be a new introduction tool.
I'm also trying to get Bean to play more to improve her general happiness. Problem is she gets stuck in her tunnel. She runs to the end to hide and watch the toy, but never runs out the other end!
I'm also switching them over to canned food (and scheduled feedings). It is better for them and I will be able to use meal time as a tool for friendly goodtimes bonding. Bean is taking it better then I expected (thoroughly licking at the very least), but Kitten is less enthusiastic. I'll try again tonight.
Overall, I feel like I have a plan now. Mostly I'm just focusing on making things generally better (especially for Bean cat) and slowly proceeding with integration. There have been fewer hisses lately.