Noise from Oil pressure guage is normal, you can hear the oil squirting behind.

The engine has solid lifters so generally is quite tappy

Accelerator pedal vibration is down to the cable, go to ford and get the replacment longer one, this was a recall

Knocking noise is the DMF, never never never change the clutch without doing the DMF, the DMF will die and yours had, they all do. Mine did as does all ST170's evertually. I would avoid replacing the fly with another crappy DMF, get a lightweight alloy one. Unfortunately a new DMF is not cheap

My ST170 made no gear box noise before i fitted my Stage 3 clutch and alloy fly so the comment on the 5th gear being noisey sounds rubbish