Thanks a lot for defining BOH a "gem" and for playing it with so much dedication!
I designed the mission X almost 6 years ago, so I didn't remember anything about it: I had to play it to provide an answer ;) I have it, but I'll make a complete walkthrough and post it later today (no time at the moment).
As promised, here's the complete answer.
SPOILER ALERT: WHAT FOLLOWS EXPLAINS ALL THE CLUES GIVEN BY THE MESSAGE POINTS.
INNER AREA
At the beginning, there are 4 automatic passages, so the player has to decide which one to take. There are also two message points that say:
By exploring the accessible areas after picking up the automapper and without taking any automatic passage, the map layout reveals to be X-shaped and the 4 automatic passages are found right at the end of the segments that the X is made of. The x = 5/4*pi clue tells us that x is about 3.927 radians. The other clue suggests to use degrees, though: x also equals to 225 degrees, from which it is easy to see that the right automatic passage is the south-west one.
MIDDLE AREA
The passage leads to an area that surrounds the areas explored previously. This is X-shaped and has 4 automatic passages as well. Beside each automatic passage is a message point. The message points say:
Given that x is 225, the expression is 225/75+A-2 = A+1. The mission briefing says "Maths and... imagination", and this is where imagination has to be used: "A+1" is to be interpreted as "the character after 'A'", i.e. 'B'. Therefore, the passage to take is the one whose message point says 'B' at the top.
OUTER AREA
Finally, the scheme repeats once more. The 4 message points say:
The result of the formula is -1000, so the automatic passage to take is the one who message point says "NEGATIVE".
