-Im not sure about the weld job someone else might have to chime in idk how to determine if its good or not.
-He wont (shouldnt) know the xact psi in each cylinder unelss he puts it in the bike and does a compression test (assuming the roller is in his possession)
-A leak down is a pressure test, it just tests for air leaks. Its important that this is done. A compression and pressure test are different.
-22 domes should be good, just do a compression test and make sure your not over 150 psi for pump gas.
-Make sure you post the jetting specs in here before you start this thing up. Pilot, Needle position, Main jet sizes