Ouch! Using a crows foot and huge wrench on that thing would be very awkward. Do you have a bench vise. That's the best way... you clamp the tool in the bench vise, then just spin the thing on.
But again, what about the BB itself? That's the most likely cause of the creaking.
Edit: Sorry, I hadn't read your post about thinking the BB was ok and that you had used Loctite (609 retaining compound?) and activator and thought the BB was ok. Aside from that, I did one where the actual lockring on the spindle was loose and caused a clicking every rotation. The only other things would be to remove and clean the chainring bolts etc., little bit of Loctite 222 (purple) on the threads, and maybe a light touch of grease on the bolt and chainring faces where those two meet (not the threads). Just gotta go through everything at this point I suppose. I presume you've checked the pedals etc.
Yes, 609. Guess it's a case of pulling the c/set apart and starting again, see if that helps. In any case the odd thing is why had the torque on the crank arms dropped noticeably in such a short space of time?
It's a Spidering so no bolts, did seem to be able to get it reasonably tight, there was a screech of protest from the bolt nipping up despite the grease, would have thought this would hold well enough with the Loctite 242
Could be the BB, hoping not!
A trick I use to keep that tool from slipping on the lockring is to compress the whole assembly (DS arm/spider/lockring/lockring tool/torque wrench) in the padded jaws of a vise. I place a thrust bearing between the head of the torque wrench and the jaw of the vise to minimize friction that will affect actual torque seen by the lockring. I wish I had had the presence of mind to take a picture when I was putting mine together.
EDIT: Calnago beat me to the vise thing.
Just a small vice that I can attach to a workbench however it wasn't adequate and twisted when I tried to put a lot of force through.