Without commenting on the settings of the OP I have to say that the standalone ABBYY Finereader program does a MUCH better job than the built-in DT OCR engine (in terms of file size, not quality). The file size difference is sometimes as great as 80%. I’ve always been pleased with the quality of the DT OCR engine, but for those with hard drive space concerns you may want to look into the standalone program.
Unfortunately, the only way to get the ABBYY that comes with the Scansnap to OCR a document would be to print it and scan it again. The engine that comes with the Scansnap is limited to only OCR documents that come from the scanner, to induce you to purchase the full Finereader product if you want to OCR general documents.