That seal leaking slightly won't cause that noise, did anyone check the oil level?
Bumps causing the noise and vibration would be shocks, wheel unit bearings, skid plates.
I didn't know that the 2017 heater hoses were gold plated, I don't have a JK that new to know what they look like but you need to find another Mechanic I think.
My Aftermarket bumpers were bolted on just like the Factory ones.
Having lockers in the front and rear would be the best for snow, but if you have a auto trans not sure you can have them.