Suggestion On Repairing Power Supply
Usually when any FET shorted or have problem the related circuit surely will have problem. This means you may need to track from the Gate, drain and source pin until you could find the bad components. if there is no bad components then you may need to direct replace the power ic that supply the gate signal to the FET. If it still the same then i suggest that you connect the original load and with the fuse and turn it on. Sometimes a power supply really need full current (bulb will limit current) and full load to work properly but in this case you may have to take the risk.
As for diode I don’t trust digital meter result. I would use analogue meter set to x 10 k ohm to test the diode off board. A good one should have one reading unless if it is a Schottky diode. A Schottky diode will have one full reading and another result would be half or less than half reading.