Just to confirm, are you referring to the homepage feed or the subscription feed? You can remove recommended content by selecting 'Not interested' on your home page. Doing this influences how YT suggests videos to you in the future: https://goo.gl/1xZ6Wn . Keep us posted.
Sure, keep us posted. Also, you may want to try removing related searches or the video itself from your history, here's how: https://goo.gl/mfD7rf