Hi,
Wow, it sounds like you're really trying very hard with your embouchure.
May I suggest a large gin & tonic, unwind and look at it from a different angle?
All this talk of 6/7/8 mm apart etc is making you too stressed.
So many people look at their instrument as though it's a holy relic and must be played in a specific way or you may get turned into a pillar of salt. It's actually just a hollow piece of wood.
The truth is that your teacher/book will give you guidelines on how to form your embouchure, but it's up to you to experiment and see what works best.
Everyone is different. Our mouths are different shapes, long/short tongues, huge/small teeth, fat/thin lips, strong/weak lungs etc.
Try this: Take in a bit more MP into your mouth, keep the instrument almost vertical, feel the MP 'behind' the teeth, not 'under'.
Then experiment with your lower and upper lip. Play a note and change the angle of the instrument. Better or worse?
Keep experimenting. Check the MP, reed, ligature and barrel. A beginner often thinks the fault lies with their embouchure when the problem is actually the reed or MP.
Above all, HAVE FUN!
Steve
PS Don't forget to put lots of little cuts into the lemon rind. The lemon oil inside really helps the G&T!