I'm going to ask my friend to stop commenting
What's wrong with them commenting?
Because he is commenting too much on my Facebook posts.
It sounds like he's been a real nuisance here. In that case, it's fine to ask them to lessen or even stop commenting on your posts since they are your posts after all.
His comments are so odd too.
It is understandable to be upset about getting odd messages. You should maybe set it so that you cannot see those messages on your feed if he doesn't stop sending them.