I like it just fine. Not too soft, but not overly harsh on the street. However, while I don't think the shocks are blown out, they have been on there a while (since about 2009).
I found out after resealing the top end on my Grand Marquis that the lower intake bolts definitely back out a bit and need a retorque after a couple heat cycles. A few of them needed several turns to get tight again.
If the ground wire is the circuit return path for the light when it's on, then yes. It will show 12 volts when the light is on. It would be helpful if you had a wiring diagram from the tach.