Yes, turning on your headlights will add increased load to the charging system/alternator, which is being turned by your engine via a belt. This increased load is increased work for the engine. If you have power steering on a 2.5L Jeep, there's even a little pressure sensor that tells your computer you are turning the wheel and will increase the engine's idle speed to compensate for the increased load of the PS pump.
Get a set of "vitals" that include battery voltage readings at rest (about 30 minutes after you shut down not right after as that will give you a false reading) during starting (if it drops below 10 volts the battery is undercharged or on it's way to battery heaven) and during running. This will give you various ideas of the health of the battery and charging system itself.
Having good dedicated grounds is never a bad idea, adding grounds won't hurt anything, it's a ground not power, now hooking your positive battery terminal to the body...........that would make for an interesting time as the firewall glowed red-hot. All the engine's sensors run on a 5 Volt reference signal. If you have old corroded battery cables, this will cause issues as the computer won't see proper values from the sensors. If you don't know how long it's been since you replaced your battery cables. Just do it. They have a finite life. I replace mine every 5 years. More than one YJ,XJ,TJ owners has chased their tails over what amounted to shitty grounds. I've had cables on used Jeeps I've bought look fine externally, but when cut apart would be a solid tube of corroded wires.
