iPod Classic skipping tracks

I have a (supposedly new) 160 GB iPod classic that I purchased from a 3rd party on Amazon. The Apple store reformatted it for me and then I synced it with my iTunes Library on an old iMAC. The library is large (10,000+ songs) and organized the way I like it with a variety of playlists and folders. Some of the music are downloaded from Mixed CD's with no track labels. So the music is stored in folders or playlists with the names or descriptions of the CDs. Any attempt to (auto) reorganize this library on iCloud by track name or artist name, etc will be a disaster!

Now that the entire iMac iTunes library is on my iPod, when playing the music it skips at random tracks, or sometimes even just pauses. The problem is widespread across the iPod library but doesn't affect every Folder, Playlist, or Track. However, it happens frequently enough and randomly enough to be a royal nuisance when listening to music. On the other hand, playing the music directly from the iMac library works just fine.

So I'm thinking that the iPod is either defective, needs a really good "rewipe/reformat", or the sync software from old iMac to new iPod classic is defective or incompatible. Regardless, if I can offload my entire iTunes library from the iMac intact and simply play it as is on iCloud, that would be great. Ideally, I want the library downloaded to my iPod so that my music is mobile and accessible at all times, regardless of WiFi availability. This is essential for my long plane trips.

Any informed or experiential suggestions would be greatly appreciated!