Relax, you are over thinking this. That fuse goes across the transformer windings and all the GI lamps so unless you pull every connector off the board you will see continuity except at very low resistance setting on your meter. A much simpler test is is does the GI light up? If the fuse is blown you will have no GI and no 6.3vac at TP4. If that is measuring 0 then yes you have no GI and the S&T will not boot up.