One thing you don't want to do is transfer too much weight to the FA. 100 lbs, probably fine, but I wouldn't go much more than that.
While it is unlikely for a reasonable person, it is technically possible to transfer TOO MUCH weight and actually take too much weight off the rear axle. This is a VERY dangerous situation. That's the only fear I would have returning MORE than unloaded weight back to the front. Of course, you want to stay within your axle specifications too, and remember that since the steer axle is also carrying the power plant, it may not be able to take a lot more weight than it already has.
As far as the weight adjustment you mention, I'm not sure I understand which specs you're talking about? Are you asking if the height of the coupler and thus the level of the trailer changes with adjustments in weight transfer?
Yes it can. One of the common misconceptions about WDH is that it is used to level the tow vehicle. So, many people are trying to use the WDH spring bars to get their truck to be LEVEL front to rear, thus changing the height of the hitch and subsequently the level of the trailer. So, yes, adjustments to weight transfer do change the height of the trailer tongue. But remember, that's not the goal. You want the trailer to be level (or slightly nose down) and the lost weight returned to the steer axle of the tow vehicle. The rear "squat" of the tow vehicle is what it is.
So, with that being said, depending on the instructions on your hitch, you set the trailer level and adjust the ball mount to be the same height, or whatever the manufacturer instructions state (Blue Ox Sway Pro says "The ball height needs to be the same or 1” higher than the trailer coupler height, adjust as necessary.") So, then you can expect the rear of the truck to drop 1-2" when hitched with WDH engaged, giving you either a level attitude or slightly nose down. If the trailer has too much nose down attitude, you need to adjust. Same if the trailer has a nose up attitude (you would rather be slightly nose down than nose up).
Anyway, I hope that helps. I had to study this stuff a lot when I first started out, and I've been studying it a lot MORE now that I'm getting a different hitch.
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!