Hi Karl. So happy to have you join us on the forum. Congratulations on your baby. Your post asks a lot of questions and, hopefully, they will get answered. First of all, you have every right to ask your roommate not to punish your kitty. First of all, cats do not understand punishment. Second of all, it can be cruel. The other thing ... Bellina needs a tall cat tree. They are not that expensive and you can find some that don't take up a lot of room. Most come with sisal rope for scratching and it can save furniture and blinds.
My cat scratches the wall around his litter box as well. It's just his thing and I would not worry about your baby doing it. Trimming nails? I don't and have never trimmed Raiden's nails. The vet has done it a couple of times when I've taken him in -- but I love having his claws razor sharp as he never uses them on me.
It is quite easy to train a bengal to walk on a harness and leash. HOWEVER .... know that once you start the walks, Bellina is gong to want to go out ALL the time. My bengal was an outdoor cat for six years. When I took possession of him three years ago, he was not happy being locked up behind closed doors. We built him a large 12'x12' enclosure on our deck that he can access 24/7 through a cat door in the dining room window. That still wasn't good enough. So I purchased a harness and leash and he took to it right away. We do two one-hour walks a day -- still not enough for him. He still wants to escape. Every time we go grocery shopping, I have to close him away in our bedroom until we get everything inside the house. You definitely do not want to simply let your cat outdoors. So many dangers out there and most indoor cats get terrified of the big, open world around them. And if she is easy to befriend, someone may take her in.
Know that bengals are challenging and are not like your regular cat. They have their quirks. Most are not aggressive unless they are being mishandled by the owner. You have no idea what Bellina's life was with her previous owners and you definitely do not want to make the same mistakes they did. She needs to be treated with patience and love.
Wand toys work the best with bengals. Keep your hands away!!! And know that many bengals do not like to be picked up and held and are not lap cats. They show their affection with head butting and staying close t you. Bengals are very vocal, especially social -- love their humans. As Jill mentioned, you have to adapt to the cat, not the other way around, so maybe training your roommates is the solution.
I hope we have helped you a little. We are here if you have any other questions. Good luck with Bellina.