Deriving an Isolated 10 volts

Yes, you're right, it's drawn backwards, it's not my circuit, I would've drawn it the other way round.

I haven't calculated the oscillator frequency but I'm sure it's >435Hz, are you sure you didn't mean kHz?

I'd recommend changing the MOSFETs to ones with a lower Ron because the ones in the diagram are high voltage and will have a higher resistance.