Signs of a bad/weak battery?

The more I notice things, the more I realize my car might have a bad battery. While my car is running, my oil pressure gauge will often randomly spike then go back to the correct pressure, and if I roll my power windows up or down it will spike up and go back to normal once I let go of the switch. My idle will also drop down quite a bit if I turn my headlights on, the oil pressure twitches when the hazard lights/turn signals are on, and every once in awhile my car will have a very jumpy idle. In addition, this cold weather sometimes causes issue with my car firing up on the first crank. I have to give it a second crank every once in awhile.

Would these be the signs of a dying battery?

Well I replaced the main ground that goes from the chassis to the engine block inside the engine bay. I noticed that it was very brittle, and partially covered in oil. This might be the reason for the issues I'm having, I'll post up more tomorrow after I drive the car.

Ironic because I had just noticed the same thing about my 95. Hit the power window switches, or turn the headlights on and off and I notice a quick drop in RPM.

Well, the new cable fixed the spiky/twitchy oil pressure gauge but I still have a crappy idle sometimes. Did it twice today actually, some people mentioned a cylinder might not be firing. I'll probably replace my spark plugs and see if that fixes the issue.

How long has it been since you replaced the wires? They are known for breaking down and arching in the valve cover holes every 20-30k miles.

I have NGK wires with 3-4k miles on them.