is it possible that something came loose with this, and can be reconnected, or that the valve itself can be cleaned?

i.e. - can it be fixed without replacing the fuel pump? if so, can you reach it without dropping the tank?

Anyone whos replaced the fuel pump on a Blazer- can you remove or fix the valve?

If you are sure the pulseator is bad, you either have to replace it, or you can substitue a small fuel hose in its place. Some new pumps come with that new little hose just for that. Theres really no cleaning this, it either has to be replaced or a little hose put in its place.

Normally the pulsator will deteriorate and split. There's no way to repair it without dropping the tank and pulling the pump.