I'll take a stab...
This is under my understanding of US LAw... First, Design Patents protect aesthetics and not functionality. The device you are seeking Design Patent protection may have some functional aspects, but the functional nature itself cannot be protected using a Design Patent, and in some circumstances, could prohibit protection via Design Patent. In contrast, a Utility PAtent application protects functionality, separate from Design.
"The Australian Patent was approved in 2007, can we lodge a U.S Design Patent for the same Invention, it is about 5-10% different from the original standard Australian Patent?"
I'll stand to be corrected...
To claim priority to the invention of the Australian Patent itself, I believe that a PCT application (one of the avenues that a US Application can be filed from a pending application or issued patent) would have needed to be filed within 12 months of the Australian Application itself, designating the US. If one was filed, and is still 'alive'/pending, there may be ways to convert a utility to Design application, or vice versa.
Re: the 5-10% difference... it really depends on the specifics (that should not be discussed here). The tests I've seen for Design Patent Infringement (that are used to Distinguish Designs from one another, and that are similar to whether something is sufficiently distince from propr designs to be accorded Desigh Protection, Obviousness aside) seem to go to whether the Designs are Substantially Similar to one another, and I believe whether one could be confused as another- kind of a Copyight-type test.
So if the 5-10% is enough that it is not Substantially similar to the other, perhaps it could be eligible for protection under Design Patent. Now, in the United States, a Design PAtent application must be filed within 6 months of any public disclosure, sale, offer for sale or public or commercial use to be eligible for protection (if not, the Design becomes Public Domain) of the invention/Design for which protectin is being sought.
"We have a Taiwan Manufacture tooled up and ready to go, the problem is we need some form of I.P even weak I.P the design Patent, so we can give exclusive distribution rights in the USA, or can we lodge a standard U.S Patent its function is the same just the design slightly different?"
The functionality must be new, useful and nonpbvious to be eligible for 'standard' utility Patent Protection. And for Utility Patent protection, the US Application must be on file within 1 year from any public disclosure, publication, sale, offer for sale, commercial or public use of the invention sought to be patented (with some exceptions).
How does in the Public Domain effect the design Patent?, is it the same as a standard Patent?"
To be eligible for Patent Protection, whether Design or Utility, an invention must be novel (new) and non-obvious (though I'll admit that I'm not entirely sure how Non-obviousness is applied in the case of Design PAtents).
Re: Other forms of IP protection, do you have a catchy mark or Tagline associated (or intended to be associated) with the product? If so, try to build that association with your product/invention, to make customers really want the product associated with the Tag-line/ mark. Think Sony Walkman, Nike Shoes, Coca Cola- all marks with competitors, but name recognition really makes (or made) them the product to have...
Good Luck.
As always, this is not to be construed as legal advice, nor is any Attorney-Client Relationship formed by this communication...