Winebottler's IE 7 looks different to my PC's IE 7
Your description about IE 7's looks is a little too unspecific to give you a definite answer. I'm guessing that you are referring to text rendering. Wine uses a few open source libraries to render texts. These produce different results from Windows' built in text rendering. Also, it replaces some (all?) fonts with free alternatives because of copyright issues. The result is that text does look different between Wine and Windows.

As for your second question, yes, you'd need to buy a separate Windows license. If you don't need to test with IE 9, you can go with an XP license. They are dirt cheap these days.