Do the other stuff first before changing the pump. I had exactly the same
symptoms and put on a brand new Bosch pump with no change, to my chagrin.
Filter didn't make a difference either. It seems like most of the time the
noise is caused by blockage in the tank, as you suspect.

Someone told me that there's a way to reverse the lines from the fuel tank,
so  that the pump is spewing the excess fuel back out through the strainer
and taking it in through the ex-return line. Anybody ever done this? It's
supposed to eliminate the fuel pump buzz by giving it a free flow.