The most efficient way to torture Hank is to stand to his left in the gap where there is no X prompt. After about 40 "ticks" of this I managed to get the red ending (though my mental health was already quite low as noted). It seems the easiest way to get this is in fact to torture Hank (the guy in the gun shop) with the flashlight (torch). Press The Serpent: Read the Deal With The Deceiver, Press the serpent, Silence the Serpent - Common Elements and Press The Serpent - continued sections of the guide, it's too long to copy them here basically you need to choose certain dialogue option when speaking with Milton. This can be easily missed as Elohim will only tell you that so many times in one playthrough. Know Your Limits: When Elohim tells you something along the lines of leave this one for another time, you don't have to solve everything now, follow his advice and go solve another puzzle instead. Basically, don't solve any Red Puzzle Gate until you have all of the Red Sigils (Tetrominos).
Hedging My Bets: Do not ascend the tower until you have collected all 49 of the Red Sigils (Tetrominos). The hardest part should be actually finding the paint can. After ending the recording, read the QR message that you recorded moments ago. Split Personality: While using the Recroding mechanic, paint a QR message on a wall. (Two L shaped pieces and a square piece.)
LOL: Type LOL using Sigils (Tetrominos) in a gate-puzzle. Regarding the ones you mentioned (text taken semi-verbatim from the guide):
You can read Elisav the Evil's Total Achievement Guide to know how to get the various achievements.