Moving from HTML text formatting to CSS pretty much requires redoing everything. There's no easy way to go about it. That having been said, most of your changes will be to table contents, to change all those nested font tags to a single style definition. Probably the easiest way to do this is just remove all the font tags:

s/<\/?font.*?>//sg;
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Then you give your table a class (let's say datatable), and define the equivalent of your font tags for .datatable td { }