Is there a way to remove older versions of var files? Some kind of tool or script
As far as I know, the most reliable way is to just regularly do a manual check of your addonpackages folder and move older versions of non-plugin VARs to a folder somewhere else on your hd (or delete them if you're sure they are not needed).
Older versions of plugins should stay in your addonpackages folder, as sometimes other VARs that depend on that particular version of the script won't work properly.
Morph packages are a bit of an exception though, and any VARs that just contain morphs can be unpacked into the correct folders, and then removed from addonpackages. Looks and appearances don't care where the morphs they depend on come from (despite the error log messages about missing VARs), so having them all stored in your custom/atom/person/morphs folder is fine.
If you do that, you'll get a load of subfolders in each of your morph folders. Merge all the subfolders in Morphs/female and remove any exact duplicates (but move ones with different file-sizes into a subfolder, as some different morphs have the same name). Then do the same for Morphs/female genital, etc. It speeds up load times and makes look creation easier due to not having thousands of duplicate morphs. Just to note that if you plan to release scenes dependent on those morphs, you'll have to include the morphs in your VAR or use morph merger to make a custom morph, or just use a separate install (with the morph packages as VARs) for content creation intended for distribution.