Just had a chance to read this thread from the beginning......the deck height and level depends mostly on how the rear links are set and that is easier-said-then-done. Not really hard, just not all that intuitive and somewhat difficult to see ......bit of playing around with a small trolley-jack (cheap Chinese Harbor Freight type work well) and you will find the sweet-spot. Then I would just leave it there if you can.
J Cummings sounds like the ball is missing from your from gauge-wheel spindles, but the main issue probably the deck not sitting or "hanging level". I recently had to completely rebuild one of my front gauge-wheel units, but the other is still OK.
I routinely use the Diff-Lock pedal (on the left) and also lock & unlock the 4WD as needed......both make quite a difference depending on situation. The Diff-Lock is a square-cut gear deal, so have to be persistent, but gentle with it several times to get it to engage.....do not force.
My hydrostatic whines also.....I wear ear plugs. I mow in Low range & WOT most of the time.
I am pretty sure the bushings in my rear axle were bronze....do not recall any synthetic or plastic, but could be wrong. My machine does crab a bit on cross-sidehills, so am careful doing that along one fence line.
Yes the steering is quick and the rear can swing around like an angry crocodile! It moves like a fork-lift, but quicker. I used to have an articulated PowerTrac and the ONLY way to drive it was with a wheel-spinner knob.....I thought of getting one for the F, but do not need it.
Good to see more folks getting on the F-series band-wagon....they are great machines (I do know there are other similar front-mowers out there - JD, NH, Iseki, Toro, etc).
Cheers, Rip