Having to code around this (see screenshot), I noticed post, post_ID, and post_id all had to be checked. It felt cluttered/inefficient. Maybe could clean that up too, please.
Again, using WP_Screen should make much of this code unnecessary.
Ok Beda contacted me with more information on that. I recognize now the screenshot you shared for the code is not part of Toolset but you wrote that custom code and as per our support policy, we do not entertain any custom programming needs.
Your point could be valid but I checked with one of our Dev and get_current_screen() is just works fine when he try to edit the Toolset form on backend (admin). Dev tested with PHP version 7.2.2 - could you please tell us what PHP version you are using?