Introducing my two cats?

[Ji Hy]

I've had a male domestic orange tabby cat for 10 years now. He's ten years old. He's the sweetest cat in the world, he loves attention and he's very affectionate..
On a whim today, we bought a beautiful female Siamese kitten. We were able to take her home right away, as we still have all of his kitten gear... tiny bowls, basket, box, toys, everything. She's very calm, quiet, but playful. She also seems to love being held and petted, everything. She's only two months old.*
We kept them in separate rooms for around 2 hours. Letting her explore around and get used to where her box, bed and food would be, and just letting them do their thing. Before we introduced them, we doused them both in baby powder to make them smell the same, and let them peek at each other through a crack in the door. She's absolutely fine with him, I suppose because we got her from a pet store, and she's still used to other animals. He, on the other hand, seems to hate her. He was hissing before, but stopped by now. But he's been growling at her all day. She seemed a little scared, he growled at her while she was eating, and she backed away and refused to go back for a while.*
How long will it take for him to calm down, or will he? I partially understand why he's so disturbed, he's been alone for 10 years. But it seems ridiculous.... She's probably 1/6 his size.*
Currently, he has her cornered behind a couch, and there's some sort of staring contest going on. Anything I can do to make this better?

Additional question: I caught him eating her food. He can't. It's kitten food, it's too rich and will probably make him sick. How do I ensure that he won't be drinking her water, eating her food, or using her box? All of his stuff is in the basement, and hers is in the main level bathroom.*

Thank you so much!