I personally think that the argument of 'The force allows you to do this and that, so THIS should obviously be possible' may seem sensible, but if carried too far, can lead to crazy situations.
I agree, saber throw in principle should be perfectly possible for even a padawan to master to some degree - if you go by what Jedi's can do in the movies.
But if you can throw the saber out, control it's path and bring it back to you, then why can't you send the saber out and just hold it there? ANd then fight people from a reasonable distance without having to physically be there to slash them? You could just hide round a corner (presumebly you wouldn't even have to poke your head round - surely a Jedi could 'see' round the corner using the force) and then float his saber around slashing whoever he likes, like some kind of phantom enemy. (In fact, isn't there some Star Wars book where this exact thing happens?)
Like you say - a light-saber hilt is small and light, it surely wouldn't drain that much force-power to do that....
However, that to me would be anything BUT true to the SW movies, even though it's 'realistic' in principle.
So for me, movie realism means just that - what you see in the movies. Nothing more, nothing less.
The only time you would break that rule is if it is ABSOLUTELY nessesary to so for gamplay reasons - but this should still be rare...