Most animal behaviorists suggest keeping the dog on a leash for their first encounter. This way things don’t get out of control.
Since the dog was there first, be sure to overdo it with praise, attention, treats etc. so that he doesn’t feel displaced and only associates the kitty with positive things for him.
It would also be a good idea to let Oscar explore all of your home for several hours without the dog to contend with before they actually meet.
This way he can figure out which places he can easily jump to if he needs to get away from doggie. That’s the advantage that cats have. They can jump out of reach where the dog can’t go.
If you allow Oscars enough time to thoroughly explore this could go a long way towards preventing doggie getting face scratched (even if the dog isn’t being hostile, but merely friendly/curious, it can get overwhelming for a little kitten.)
But if he has a few escape places to jump to, he will likely prefer that over a confrontation.
Also, if your dog is typical , he will find cat food absolutely delicious so probably best to find a higher place to put Oscars food so he can eat in peace.
Once Oscar gets familiar with his new digs, the two should get used to each other without too many incidents. Cats usually know how to teach over eager dogs how to mind their manners.
Whether they will become best friends or merely tolerate each other without warfare is basically up to them. It’s good that Oscars is so little. Hopefully Russell will feel protective towards him as long as he doesn’t perceive him as a rival for your love and attention. Just keep giving him (the dog) plenty of extra attention and praise whenever the cat is around and it likely will be fine.
BTW: Oscar is adorable. Do they know if either parent was part Abyssinian? The reason I ask is because of the big batwing ears which are typical of Abbies. Hopefully he will grow into them more as he gets bigger.
I had a Calico that must have been part Abby because she had the biggest ears I’ve ever seen in any cat I’ve ever had. But she wore them with style and it made her quite a unique little character. She was also polydactyl (Hemingway cat) on her front paws so they looked like big mittens. So that became her name, Kitten Mitten, RIP sweet girl.