I don't think the process given above is going to help. Moving the media folder breaks iTunes connection to the files, which it then cannot consolidate, or play! 😮
I'd advise you add the iTunes Media folder to the library, so that iTunes is connected to all files, then dedupe as set out below. Given all the duplicates will have been added today sorting exact duplicates on date added will allow you to easily select and delete the duplicates, which you should send to the recycle bin.
Apple's official advice on duplicates is here : Find and remove duplicate items in your iTunes library. It is a manual process and the article fails to explain some of the potential pitfalls such as lost ratings and playlist membership, or that sometimes the same file can be represented by multiple entries in the library and that deleting one and recycling the file will break any others.
Use Shift > View > Show Exact Duplicate Items to display duplicates as this is normally a more useful selection. You need to manually select all but one of each group to remove. Sorting the list by Date Added may make it easier to select the appropriate tracks, however this works best when performed immediately after the dupes have been created. If you have multiple entries in iTunes connected to the same file on the hard drive then don't send to the recycle bin.
Use my DeDuper script if you're not sure, don't want to do it by hand, or want to preserve ratings, play counts and playlist membership. See this thread for background, this post for detailed instructions, and please take note of the warning to backup your library before deduping.
(If you don't see the menu bar press ALT to show it temporarily or CTRL+B to keep it displayed.)
The most recent version of the script can tidy dead links as long as there is at least one live duplicate to merge stats and playlist membership to, and should cope sensibly when the same file has been added via multiple paths.
As for not consolidating all of your media I suggest a quick skim through Make a split library portable. A portable library is much easier to move, backup or restore. Having iTunes connected to files located outside of the media folder rather than inside won't have a positive effect on performance.
tt2