Yes, your videos affect your rating.
If the video is deleted on Youtube / Vimeo, it won’t be available in the “Video” section and deleted from it after a while (the exception are publications where the video was an addition to the post).
Yes, you get views (but this is not the reason to spam your videos).
You can add videos only from Youtube and Vimeo.
To add the video you need to publish it on your page or in the bike blog.