It's a pain I know @Wildridedesigns!
It's one of the things that just makes the experience difficult but it's more of an issue on Facebook's end, it seems they don't import efficiently from Square and make an irreversible mess of it most of the time or at least a mess that has no easy fix, what you could do is export your item list (as CSV/Whatever it lets you, I can't remember) and upload it to Facebook and see if it'll work that way?
Hope this can help in some way, but yes, I too end up having to individually add most products...
