Most PCs have a screen resolution from 75 to 100 DPI. Such a resolution will indeed look poor when printed.

To get a print quality scan you'll scan at about 300 DPI. If you don't let your word processor scale the image it will again look quite strange. But if I scan at 300 then make it fit, the printout looks good.

As to filesize, scans in TIF or bitmaps will be quite large. Nothing wrong there. Try JPEG next time.

Epson and other companies no longer teach how to use their products on the support lines it seems. Hope this short response gets you going.