Dead satellites do add a much larger risk than satellites that can be steered, sure. If we stopped steering all our satellites right now, I believe it'd only take a few days before a collision occurred.
However, every satellite in orbit adds to the risk, especially if a chain reaction starts happening and it becomes very hard to avoid the shrapnel flying around. Or if a once-in-a-century-type solar flare takes out a bunch of satellites.
Edit: Basically, the best way to prevent Kessler Syndrome from occurring, is to keep the number of satellites in orbit below the threshold where it could occur.
Depends. If you use Google docs or the browser version of Office 365 (or whatever it's called now) you'll be fine. If you want to use an offline document editor, you'll need to be technical enough to understand the difference between file formats like doc, odf and pdf.
If you receive a doc file, edit it in LibreOffice and send it back, the recipient might complain that the layout has shifted slightly.
If you need to be absolutely sure the recipient gets the document layed out exactly as you created it and they don't need to edit it, exporting to pdf is a good option.
If you need to send or receive Excel/spreadsheet files you might have a bad time, I think. Though interoperability there may have improved since the last time I tried that sort of thing.
Before switching to Linux, download the Windows/Mac version of LibreOffice or OnlyOffice and see if it suits your needs. If not, it should be possible to run Office 365 on Linux using Wine or Winboat. However, Wine might not work or require too much tinkering for the average noob. Winboat should be more foolproof, but will increase the startup time of the application because you're running it inside a Windows VM.