throttle stop adjustment, Pressure Regulator housing broken - merc 250 3.0 EFI

new to me project. When looking over engine, noticed a couple of items and hoping some can assist:

1. the motor has a throttle stop adjustment on the linkage on the motor. If I manually open the throttle, I notice the top butterflies are not completely open. About 30% left to make WFO. Is this something I can adjust or is this a normal situation?
2. The vac line that goes to the fuel pressure regulator is not attached, easy fix. I assume this controls the return line pressure?
3. The assembly with the schrader valve(to check pressure) is cracked at the base where it mounts to the block. Is this a part I can get my hands on?

Engine has 300 hrs on it. I am planning to have heads cut, reeds replaced and have Simon do the boxes. Want to take this to 300PM levels.

Thanks in advance