I know you're trying to keep the cats separated for safety but I think you should slowly introduce them to one another. swap their territories so they learn each other scent, then lit kitty roam free while holding older male. When I introduced my kitten to my older male 6 years ago I held her in...
Hello!
I had a very similar story. I rescued my cat at 3 months and she was uninterested in scratchers, cat beds, etc. Noticed she hated cold floors so I got a flat scratcher with that wiry straw like material for 1$ at the dollar store and put it in the middle kitchen. She'd find it and sit...