Q1 - do you rely solely on a sleeping bag /pad when hammocking in cooler weather (below 50)
I hate sleeping bags. No.
Q2 - do you use a pad with an UQ
If it got cold enough I might. Haven't had to - I generally overnight in temps 25F - 40F.
Q3 - do you use an UQ with a bag or without (not counting bags used for TQ)
What? Are you asking if we use a bag as additional underside insulation? because that doesn't work - stuffing things in the UQ only makes it sag and become ineffective, the bag would have to be modded to be an UQ.
Q4 - if using an UQ, what do you use for top coverage (i.e. open bag, TQ, blanket, etc.)
My other quilt. It's just like my underquilt.
Q5 - if not using a bag, do you use any bedding in the hammock (under you)
Other than the UQ or pad, no.