You are close, but you should be ok, I think.
Theoretically, you should not adjust the front to be compressed more than unhitched. But, 1/4" is so small that it could be measurement error. Also, theoretically the adjustments should be done with both truck and trailer loaded. But I know, that is not all that easy. It would be tough to tell my kids to sit still in the truck for two hours while I keep on adjusting - hitching - unhitching - adjusting .... LOL. How many washers did you need to get where you are?
The only way to really know is to go to a scale and weight it, all axles. Then let us know here what the numbers are. I go to our local landfill when we head out sometimes, they let me use the scale for free (they don't have much of an option when you drive right onto it, I guess, lol). Go on there with all axles. Record the reading. Drive the front axle off the scale. Record the reading. Then drive the rear axle off (now only the trailer is on the scale). Record. That will give you a very good idea. The only number missing is the tongue weight (and therefore total trailer weight), but you'll know axle loads, GVW and GCW. To get the tongue weight and axle weights you'd need to unhook.
Have fun on the trip, and let us know what the numbers are when you go to the scale. Yes, you are probably right at your GVWR (maybe a little over) with only being at under 60% of the tow rating. The GVWR is the most limiting number for our trucks and it sucks.
Oh, and I do think that you are very likely over 3,500lbs for the trailer. Your 176RB is rated at 3,370lbs dry, right? That does not include any options, no A/C, no batteries, no propane tank, no cargo. Measure it. There is almost no way you are at 3,500lbs. Mine is rated at 3,615lbs dry, and we were at right around 4,200 with no water, and very little cargo.
One more thing: if you installed the WDH yourself (and it sounds like you did), then you are most likely better adjusted than 90% of the people who have that done at the dealer.