I know this feeling. When I was stalked and harassed by an ex over email, everyone told me to change my email account. I refused, however, because it is a Gmail account which is connected to my Google Plus business page, and if I got rid of that account, so would my business G+ page which I need for work. I had spent time building up that page and all my business connections.

Don't give into the temptation to not post on your business page because of him. Then he wins and you lose, and he has power over you.

See if you can block him there or remove him from being able to like, comment or access that page.