I've tried re-downloading and repairing via WinRar, but it seems the following fonts are missing the .ttf file completely when I view the list of files within the .zip. I get an error when trying to extract them, either "The archive is either in unknown format or damaged" or "Unexpected end of archive".

Unable to unzip (corrupted??) the following Fonts:

http://www.dafont.com/all-ages.font
http://www.dafont.com/scorched-earth.font
http://www.dafont.com/bernalheights.font
http://www.dafont.com/polar-vortex.font
http://www.dafont.com/rfx-splatz.font
http://www.dafont.com/charnel-house.font
http://www.dafont.com/damneddeluxe.font

I'm able to install other fonts so I don't think it's me.

I've download and unzip all.
I think that the problem is that's very heavy fonts, difficult to use, with a long time to display for an old system.

Are you on WiFi? If so, download again but this time with a cable connection.