Hi Michael, welcome to the forum! Your Oscar reminds me of my Joker, who is supposed to be a rat terrier, but my vet suspected he had some basenji in him. I loved your video, and you seem to be the type of person filled with positive reinforcement. Whether Oscar has basenji or terrier in him, I think it's important to give high praises when he does his business outside, to include loving scratches behind the ears, lol. On the other hand, if you come home and there's been an accident, I wouldn't "rub his nose in it", but I would carry him over to the spot and gently scold him, "Oh Oscar, what did you do?" And then I'd promptly take him outside and when he potties, high praises again.
Think of Oscar as a 4 year old child… while they don't necessarily understand the words, they understand when you are happy or sad. He is in good hands with you, and with time, he will behave better inside... but I agree with others that it would be good to get him neutered.
Hugs, wags, and roos! 🙂