Based on the log files provided, I believe the issue is related to the fact that the OP has a so-called "portable" install of Bitcoin Core... and Armory is simply unable to find it (not in default "Program Files" location etc.)
I've only been able to replicate this exact error ("BitcoindError: bitcoind not found") by having Armory set to "Let Armory run Bitcoin Core/bitcoind in the background"... and not having the correct folder locations specified:
If that setting isn't checked, I just get: "2018-11-14 11:18:19 (ERROR) -- ArmoryQt.py:1878 - Bitcoin installation setting is a non-existent directory"
So, my advice would be to tick the box and put in the correct paths:
"Bitcoin Install Dir" = Path to where your Bitcoin Core "Portable" dir is... (NOTE: Armory is expecting bitcoind.exe to be in a subfolder named "daemon")
"Bitcoin Home Dir" = Path to the Bitcoin "datadir" (this folder will contain the "blocks" subfolder)
ie. if you have your portable Bitcoin extracted to "E:\portableBitcoin" then your "Bitcoin Install Dir" should have a structure like this:
E:\portableBitcoin (should contain bitcoin-qt.exe)
E:\portableBitcoin\daemon (should contain bitcoind.exe and bitcoin-cli.exe)
If you plan on starting Bitcoin Core yourself (because you want to use the GUI for something)... you can actually have the box unticked and it should work OK, IF you have the correct paths showing in the 2 boxes (ie. "open settings -> tick box -> enter correct paths -> save -> re-open settings -> untick box -> save")