Oddity 1:
In my library / Puchased it shows "Resident Evil 7 biohazard" as Not Installed.
Selecting it here shows Buy $29.99
Selecting it on the dashboard shows Play with the disc.
That's normal behaviour in the Library, which I'll come back to.
What you are getting confused over is that the disc game is INSTALLED not PURCHASED.
The PURCHASED section is only relevant to digital download games/content .
ALL the DLC (except I think the Chris Redfield dlc, that can be purchased from the store for free) is included in the Gold edition.
The quirk of the library is that under INSTALLED games, you'll see two entries for a game you have installed from disc when there is dlc installed/available; the disc version, and the digital version.
It adds the digital version as you have relevant dlc tied to that game.
IGNORE the digital version unless you want to purchase that as well. It will still show all the available/installed dlc even though you don't actually own the digital version of the game.
I think your other two concerns are a direct result of the confusion over the first point.