-mild scraping. Check the brake calipers. I have a recurring stuck caliper that doesn't seem to cause any driving or braking issues, but I can hear it scraping very slightly against the rotor.
-shudder: Check tires out. Could be a flat spot or busted belt. This would cause shuddering when weight shifts like acceleration or breaking. This would also cause a noticeable shudder in the steering wheel.
-alignment: probably a tire issue, likely related to the shuddering.
-headlights: maybe a wiring issue. I would check the connections and try hooking up a volt meter and see if there is power to the wires.
-coolant on ground: I would get this checked out immediately. My wife's 07 GT just did this a little while back and it ended up being a blown head gasket. The coolant was leaking on the passenger side as you described.
-door locks: probably not a remote issue. Possible wiring issue.
Do you know if the car was ever in a flood? Lots of random wiring issues might be a result of some corrosion.
2009 Techno Gray Metallic G6 GXP Sedan (3.6L Auto6 112K miles)
CRAB Intake Opt 3 w/FPU, Lloyds GXP floor mats, HIDs low 6000k 55w/fog 3000k 35w, LED DRLs behind lower grills, V3 Triton LED turn signal/reverse/brake, LED side markers/maps/dome/tag/trunk/high mount stop, 2 coats niteshades on tails, Tint 35% all around, Debadged (except arrows), PAC IPod and BT adapters, PowerStop D/S rotors and ceramic pads, Resonator repl w/24" cherry bomb, Racingline STB, Big 3 Upgrade, Optima Yellowtop D75/25, Blacked out arrows, chrome window trim and black dipped wheels, KYB struts and shocks, CM lowering springs, Cherry Bomb Vortex Crossflow muffler, 2.5" pipe from axle back, two 4" stainless double walled slant tips