If you quit YouTube then you also quit all the content on YouTube that isn’t elsewhere. The best solution if you still want to use it is to use 3rd party apps. Personally I would actually count that as having no reliance on Google in particular anymore. If a video platform owned by Google wasn’t the most popular then it would be another platform. I don’t think you should think of 3rd party apps as YouTube frontends, but rather, apps that scrape videos hosted on Google’s servers.
I believe there is more functionality that is supposed to exist beyond just the cross platform search, but that functionality depends on the cross-platform identity thing I mentioned.
Yes.