i think my mac is infected

i downloaded a torrent for an app and proceeded to try to install the app, ignoring the red flags every step of the way: i shouldn't be torrenting in the first place, the torrent was posted today, had a suspicious amount of seeders/leechers, wanted to install adobe flash player with my password, proceeded to rapidly open safari, chrome (to change search engines), etc., then didn't install anything at all. still not cottoning on at this point (i just thought it was weird that nothing happened) i immediately tried to uninstall everything i could (the changes to chrome & safari, adobe flash player) but couldn't remove the installation app from launchpad. after googling for a long while & trying several things, i finally realized that i had infected my mac, i'm pretty sure with iworm.

since this realization of my stupidity, i have run sophos and malwarebytes anti-malware & removed any threats that they detected while scanning. however, sophos detected some adware i'm positive the malware installer installed on my mac today that malwarebytes did not. i'm paranoid that my mac is still infected with some other threats. do i need to completely reinstall os x? can i safely transfer my personal files (photos, docs, etc.) to cloud storage sites? also, an external hard drive was plugged into my mac at the time of my stupidity; though it's an ntfs disk, is it also infected? if i'm fine with erasing & re-installing & starting over as if my mac is fresh out of the box, do i need to do a back up?