Yes, I'm diversified value (of sorts) but I place much more emphasis on companies with strong brands (so I place more value on intangible assets than PYAD-style value). Plus anything up to about 15% of the portfolio can be in very high risk stuff (mostly small oils).
FTSE prices are taken from Yahoo! Finance. For the dividends I've assumed that they are the the FTSE dividend yield but spread equally across the year (i.e. return = FTSE yield x days since 1st Jan / 365).
It's a rough calculation but as Keynes said it's better to be roughly right than precisely wrong!
I'm afraid that I can't be of much help as every broker I've ever dealt with uses W-8BEN forms.
You could try contacting the Internal Revenue Service (IRS), but they aren't the easiest of organisations to deal with.