kya - that alot of lube you are using. I just dip the spoke threads in 3 in 1 oil and that it. You have spent too much time preping and maybe all that lube is helping you spokes unwind. This is unlikely though.
What spokes have you used? If they are lasers or similar then it may be that the spokes have extended a bit when riding. Lasers do need very persistant grasping of pairs of spokes when tensioning to ensure they have been stretched. This is particulaly important for the NDS spokes that are under lower tension or in uses they will stretch a bit and tension can then drop. When building with laser I have fully tensioned the wheel graps pairs of spokes and seen the tension drop by half afterwards.
I have never used threadlocker, even on a low tension builds 1100N DS and ~480N NDS, never had issues yet. Also your front wheel tensions are higher than they need to be. 900-1000N of tension is sufficient on a front wheel. Front wheels build without threadlocker and have tensions below 900N can develop true issues.
The park tension gauge is actually good enough for tension measurements.
I'm note sure how I'm using a lot of lube? I've heard it mentioned here to grease the spoke holes on the rim -- should I not be doing that? Then I'm dipping the spokes in a light oil, much like you are.
Spokes used are Lasers and Races (DS only). During the build I do regularly squeeze parallel spokes. Is this what you're referring to when you say "grasping of paired spokes"?
And yes, I do realize that the front tensions are high, but if tension keeps the spokes from unwinding...I'm not sure why they're still unwinding.
As far as the Park meter, it seems to be a bit more consistent after some lube and some time to break in. When I first started, the tensions were all over the place. I could measure the same spoke twice and get 2 totally different results.