If the pump starts failing, it would IMO also have a noticeable influence on the car's starting and driving.
This is not the case. It starts and runs without hesitation.
Although this is not proof of the proper pressure, it shows the pressure is well enough to keep the car going.
The only times I heard the fuel pump buzzing/humming before was when the tank was almost dry.
I have noticed a couple of times (after filling the tank) that the fuel gauge needle was jumpy, which could mean spikes in the supplied voltage). The needle jumped to far over the 'full' signal, dropped to about 3/4, returned to normal full and repeated this behavior a couple of times.
There's no signal of the MIL so, if this is something that is part of the monitored system, it seems to be within acceptable limits.
I will check on the voltages at the supply and pump side of the switch.
I do have a fuel pressure kit, but that's for another type of car (early 80s oldtimer) and I may not have the proper connectors to do the test on the TS.
I'll report back once the tests have been performed.
Thanks for the suggestions.