More than 20 million families will be spared an extra $2,000 tax hit on average after Congress excluded them from a higher alternative tax originally aimed at untaxed multimillionaires. An eleventh-hour 352-64 vote on Wednesday to put a one-year freeze on growth of the alternative minimum tax shields many middle- and upper-middle- income taxpayers from first exposure to the tax. In 2006, it affected 4 million. President Bush plans to sign the bill into law. Republicans, backed by a presidential veto threat against any tax increase, insisted that the AMT was never meant to affect millions of people and thus...