2. How are people here already reporting extended experiences with 1.4? I can't find it, and I see comments saying it's still at least two weeks away.
From the 1.4 patch notes, which may be found in the GalCivIII Support subforum:
To enable the patch, do the following:
Select Galactic Civilizations III in your Steam Library list
Right-click and select Properties
Select the BETAS tab
From the dropdown, select opt-in and click Close (if you don't see this option, restart Steam)
Steam should pull down the changed files; if you ever want to go back, do the same as above but select default
Please note: The opt-in is an early preview of the next update and you might experience bugs or other issues. We encourage players who try the opt-in to report any issues to the support forum or via support ticket so we can address them.
As far as checking what DLCs you have installed goes, the only way I know how to do it is to look at the install directory and see what's there. Some of the DLCs have subfolders in the Galactic Civilizations III\DLC folder. Some of it might have also ended up in Galactic Civilizations III\Game\Data, though what exactly I don't recall.