Same content, different target area SEO

[SEO_MediaInno]

So ok, I have a gambling site that i want to target for Australia, Canada, USA and England separately and still have .com for world wide (or not, read further).The websites content will basically stays the same for all of them, perhaps just small changes of layout and information order (different order for top 10 gambling rooms)

My question 1 would be:

How should I mark the content for Google and other search engines that it would not be considered "duplicate content"?

As I have mentioned the content will actually BE duplicate, but i want to target the users in different areas, so I believe search engines should have a proper way not to penalize my websites for trying to reach the users on their own country TLDs.

What i thought of so far is:

1. Separate webmasterstools account for every domain -> we will need to setup the user targeting to specific country in it.
2. Use the hreflang tags to indicate, that this content is for GB users "en-GB"  the same for other domains more info about it http://support.google.com/webmasters/bin/answer.py?hl=en&answer=189077
3. Get the country specific IP address (physical location of the server is not hugely important, just the IP)
4. It would be great if the IP address for co.uk is from different C-class than the one for the .com

Is there anything I am missing here?

Question 2:

Should i target .com for USA market or is there some other options? (not based in USA so i believe .us is out of question)

Thank you for your answers.

T