The fuse will be largely un-affected by the 450kHz current ( as reasoned and shown above ) - not several times the DC resistance as you posited,
putting the fuse right by the fet drain allows a high speed fuse to be used - as the peak current in the fuse will only be that determined by the power circuit and control,
thus, if the rms and/or peak is 10A, a 15A fast blow fuse would be ideal - it would likely save the semis in the event of: - sustained shoot thru, other semi failure, choke failure, sustained short ckt on the output along with control failure in the current limit.
Easy Peasy