I haven't heard of installing it in safemode but that doesn't mean it wouldn't work. If tech support guides you through it, it shouldn't be too difficult to try and shouldn't hurt anything.
Here are some other things you might want to try:
Try reading this thread?
https://www.mobileread.com/forums/sho...+sony+software
I believe some people got it working after disconnecting their computer from the internet/network. Post #44 talks about enabling/disabling DEP.
Here is another thread on how to uninstall the software. In versions prior to 3.1, there were a few hidden files/folders that need to be manually deleted even after preforming the regular uninstall of the software. Not sure if this still applies to version 3.1 of the software but might want to take a look at it.
https://www.mobileread.com/forums/showthread.php?t=55041
I believe quite a few people don't even use the Sony software and use another ebook managing software like calibre. I believe you only need the Sony software if you plan to purchase books through their website.
https://www.mobileread.com/forums/forumdisplay.php?f=166