Missing exhaust heat shield can be a culprit in "helping" the resistor pack go bad, due to excessive heat.
A/C on "max" should give you high speed fan operation - MUCH "noisier" than low speed operation as a reference point. SO, if you don't see/hear them come on quieter than that (like when idling in the drive on a warm day to test them) you aren't getting low speed operation.
In "normal" operation the gauge will go at LEAST as close to red B4 fans start cooling it as it is close to cold in normal operation when the thermostat opens. this gives a WIDE swing on the gauge that can be scary the first time you notice it. IF the low speed isn't working, it'll probably go into the red B4 the high speed cools it down, since the temp is climbing quicker than normal at that point.
In other words, the first description of the gauge readings MAY be normal - but you SHOULD confirm low-speed fan operation for peace of mind....