Is it safe to use NMM to install and change load order of manually down loaded files from NEXUS?

I have 0.19.0 installed and when I try installing with NMM I always get an error saying the file does not exist (but I can sill dl the file) plus all files show No Data under Version number.

Both of those problems are because the Nexus is under heavy load right now. It really has nothing to do with NMM itself.