Oscar,No rule of thumb, typically Australia represents 1.9-2.5%...

Oscar,
No rule of thumb, typically Australia represents 1.9-2.5% of a films budget, so you can work your offers based on this, but should always offer what you think it is worth and no more. Do your P&L's and the offer either gets accepted or not.
In most cases the film would have already been licensed before the US release, in particular if it is a high profile production with a lot of interest.
Very difficult to orchestrate a worldwide release, the studio's can do this if they control the rights for the world, but when you are licensing an independent production (i.e. not produced by the studio) the film will be distributed by different distributors around the world, so there is no hope of pulling a universal release together. No doubt, the studios with their own productions can do this and they have been to varying degrees.
ACCIDENTAL HUSBAND could perform well, RIGHTEOUS KILL has been licensed for a big sum, question mark over it, the other titles listed on the website are marginal and will face an uphill battle.
Cheers.