My brother helped me do this just this past sunday, 13th. We removed and replaced the (rear drive unit clutch kit) Part # CV6Z-4A232A.  Took us about 2 hrs. Mine was shuttering and sort of not releasing going around corners under light throttle, the part cost $638.00 from Lakeland Ford of FL. Pretty straight forward R&R, only thing is you have to >pair< the new unit with Forscan, with a new 4 digit code, that took almost as long as the install. Very happy with the results of repair, (bluey) is as good as new now! This was with 145,xxx on the odo, and its a 2014 3.5 litre.

2019+ got AWD disconnect is one difference, even it that doesn't mean the change is in the PTU.

I did a quick look for the recommended PTU fluid for a 2010 Ford Edge.   Indeed, it states 75W140 so I would not deviate from that either.   My guess is that the main difference between the 2010 PTU and the 2020 ( maybe 2019+ ) is that the newer PTUs have tighter tolerances, hence the factory calls for a thinner gear oil. Other than that, not sure why they would change gear oil weights 

I would not deviate from the oil weight listed in the owner's manual - is that what's being suggested? 

Mine calls for 75-85. Also I noticed the PTU on the ST is called a high torque PTUSpecifications - Power Transfer Unit - 2.7L EcoBoost - 2022-2024 Edge.pdfSpecifications - Power Transfer Unit - 2.7L EcoBoost - 2022-2024 Edge.pdfSpecifications - Power Transfer Unit - 2.7L EcoBoost - 2022-2024 Edge.pdf, although they look the same. 

Have a local mechanic (was a Ford technician, worked for couple of dealers before going out on his own.)   Had him rotate tires, change the engine oil, transmission fluid, PTU oil, and power  steering fluid. Will change brake fluid next year, and new water pump (etc.) around 175,000 miles. (He drops engine and changes everything while its out.)   Asked  for a good look over and told him to just go ahead and fix it, no need to call unless going over a grand. He said he checked everything and couldn't find anything to fix. Really appreciate an honest, qualified mechanic. 

I guess the 2020 units are more " sensitive ".  🙂

The 2010 just like my 2017 the PTU takes 75W-140    I use AMSOIL SEVERE GEAR® 75W-140 100% Synthetic Gear Lube    

Sorry to hear about your new hair gel, etc.  Been there, done that before.   It can be a real mess.   The Ford Dealer is full of it.  " Lifetime " is a relative term.  What does "Lifetime " actually mean to the Dealer? In many cases, " Lifetime " refers to how long a manufacturer estimates how long car will be on the road, or maybe just under warranty.  So, 5 years?   The better way to drain any fluid from the car is to start with the car level.  It does make a difference.  Not doing so can leave fluids back in corners, cavities, etc., where it will stay nd not come out, leaving old fluid in there, which you do not want.   The Ford Edge PTU calls for XY75W85QL, which is a 75W85 weight fluid.  Your 75W140 is way too thick.  This can cause damage to your PTU.   I suggest doing it all over again. Make sure the car is level when you suction out the 75W140 and pushing in the XY75W85QL.   Options for refill: Red Line 50104 75W85 GL-5 Hypoid Limited Slip ( Full Synthetic ) Motul Gear 300 75w90  105777 ( Full Synthetic )   When I did mine last year I pulled all the old fluid out 14 oz ( 414 ml ) and put in 16 oz ( 473 ml ) before I got a slight drip from the fill hole. I had virtually no mess.   You can do it.

How far worn are the tires? A lot of them will become more noisy as they wear.  I have chased wheel bearing and tire whine and I feel your pain.   As a side note, when they used to ship cars by train, they would cinch them tight with chains. All of the pressure was put on sometimes 1 roller of a bearing set. The race would sometimes pick-up a small dent and the roller a flat spot. Those were only found by replacement.