I think now you should think about security. I know of a science page doing really well monetizing his blog with page fans. Most of his content are copied so not doing well in google search but he have a army of fans in fb. He average 7-10k likes per post and you can imagine the views on his blog post. Mostly are tier 1 fans when I read the comments.
A years ago this page started to post adult content for a day or 2. The page is flooded with images linking to porn sites. His account was hacked and when he regain control, he apologize to the fans but had already lost many fans. Within a month this happened again and the whole page is gone. Not sure fb or the hacker took it down. He did restart the page and is now having about 17,000 fans compare to previously 1 million over. I think now he is not making even 2% of what he used to make.
Having 4m fans in your page, you should start looking at tightening your security.