Regarding Nato, I was shocked when I saw how many countries were not paying their way as agreed. And you're talking big countries too. Trump did have a point on that. Every Nato member should be paying their way.
I think there is an element of Trumps unpredictability that helps scare some of the dictators. But I'm not convinced Russia is one of them. I wouldn't be surprised if Trump will sacrifice Ukraine for the sake of the rest of Europe in a deal with Putin. Im not sure Trump will want to go down in history as the president who caved to Moscow to be fully in their pocket, but there might be a deal on Ukraine.