Oh man you are leaving a ton of money on the table if your page is niche base.
1. You could sell the page but you will loose more money compared to monetizing it.
2. Due to the fact that Facebook pages don't show your post to more than 3% of it's followers , you won't be able to earn much from it, so the best way is to create a Facebook group with Same name as your Facebook page and then create a pinned post on your page letting your followers know that you have a group and would want them to join the group in other not to miss any of your post .