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I agree with Chappy here. But I suggest as a quick experiment:
* Set up a fresh local install of 2.0.16
* Install your custom modules
* Restore the database tables for individual modules and test.
That will give you a quick idea of whether the modules are compatible with 2.0.16 or not without investing a lot of time.
If it seems to be working out, then you can try to upgrade the core on your remote site and then hopefully you'll be working back with a mainstream core.
With the modules, take a look at the database structure for the custom modules and their mainstream equivalents (where available) and see if it is the same. If the fields and data types are identical then you can probably just restore the tables into the mainstream modules directly.
If they tables *aren't* the same then this is where things get more complicated. Some of your modules like WF-downloads are the ancestors of the current versions. If the changes in the database structure were made in more recent versions of the module, then you might be able to restore your tables into a older mainstream version that has a compatible database structure and follow the upgrade path from there.
Otherwise, you can try to map the important database columns in your custom modules into their equivalents in the mainstream version using phpmyadmin or an sql query to avoid the pain of cutting and pasting. Try the easy stuff first
but if it doesn't work out let me know and I'll try (emphasis on *try*) and help you with it.