Hi, welcome and thank you for your question. My name is ***** ***** I am glad to assist you today.
I am very sorry about your issues. To answer your question, YES, this can be done. Someone with a Facebook account can create a page or account with fake information and altered or modified timestamp.
This is NOT done directly in his Facebook account. This is done using online tools that are built just to do the "faking".
The well known tool that your ex could have used is the so-called The Wall Machine. The site's link is "http://thewallmachine.com/".
With this online tool, you can CONNECT your current and correct Facebook account to start creating a FAKE one. The fake stuffs that you create can be a fake picture, a fake status, a fake location, and most importantly, a fake timestamp or the post date or comment date. I believe your ex could have used this online tool.
There are several other online tools to facilitate the faking of a Facebook page or wall. You can also check them to compare to what your ex has. Then you can conclude which tool your ex could have actually used.
Here are the other online tools:
Status Clone => http://statusclone.com/
Simitator => http://simitator.com/generator/facebook
I hope that helped.
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