wiper switch/dash problem

IVR = instrument voltage regulator. OEM was a mechanical instrument voltage limiter.
Most are housed in a canister and plugged into the back of the panel. Others are inside a gauge, either fuel gauge or temp gauge depending on model. I don't think it is the root of your problem, just another symptom.
I just recalled some panels have only 1 indicator for both left and right turn. Even if that's yours, that bulb coming on with the wipers is just strange.