I also agree with the < 50NL stuff said. Though understanding why this strategy is as good as it is should help controlling your own game at any stake.

About the 3-betting 1/2 or 2/3 or whole raising range of your opponent, would you consider 22 be above AK in that range? Where is QJs or 46s placed? Kxs?

Isn't the difference in preflop raising range and 3-bet calling/4-betting range of most players wide enough and therefor our FE large enough that 3-betting any hand would be +EV as long as players don't adapt?
Do you know anything about a breaking point?

The guide tells us to call 3-bets with TT+, AK in position only. We should never call 3-bets OOP?
SC's are no part of our calling range, though Sauce in a comment above you put SC's in villains calling range.
Could you explain why we shouldn't be calling with them in position? (I'm still with this 25% hitting flop thing in my head)

The guide doesn't say anything about difference in 3-betting ranges in and out of position. Though 3-bet calling/4-bet ranges of villains usually differ IP and OOP.
Could you comment on the following thoughts;
- I am more inclined to call instead of 3-bet in position because there are a lot more ways to outplay villain in position.
- I am more inclined to 3-bet in position because villains 3-bet calling/4-betting range is tighter OOP so I have more FE.