Where is the best place in the world to open a Interactive Brokers account to minimize tax. Since IB requires proof of residency in the country the account is opened, it will have to be a location where residency is easy to procure and also a place where IB account can be opened.
If you are american, too bad for you on that matter if not there are many countries that have no taxes on capital gains which you can use. You can set up an offshore company and the same agent should be able to get you the necessary documents for the company, bank account and IB account opening. Probably getting some kind of bank/utilities statements in the country of your choice if you want to open the account under your personal name is enough. BTW reading your post it's likely you will be cheating your country of residence tax department when not declaring the income made through this IB account, so be careful with what you are doing.
Are taxes really that bad that trading would still be profitable after producing and maintaining residency in another country? imho If you can do it go for it! You may even get away with having a vacation spot in your new country of residence to trade from.
Income/profit is Tax-Free for most of the countries http://www.elitetrader.com/vb/showthread.php?s=&threadid=217418
Go into the link and it'll tell you under what few circumstances you can withdraw without penalty. http://www.money-zine.com/Financial-Planning/Retirement/IRA-Withdrawals/