Measured 0 Ohm's, well 0.2 of an Ohm.
That's about right.
Are any of your test's valid for when the transistor is on the board?
The only valid test you might obtain, but may not be accurate, is the bias test. You cannot do the leakage test while the transistor is in circuit. Other components in circuit will give you false readings.
Because the diode test comes out lower and it measures 1.2 MegOhm in the leakage test.
False readings as you obtained above.
Some how I don't think your problem lies in this transistor. It has to be something else. What it is I couldn't guess, but I'll keep looking into it further for you.