Epson Stylus SX525WD: scanner resolution can only be 75, 300, 1200 and 2400

[Frédéric Bron]

I have F17 installed (3.6.9-2.fc17.x86_64).
I installed the Epson driver for my printer from http://download.ebz.epson.net/:
yum install epson-inkjet-printer-workforce-635-nx625-series-1.0.1-1lsb3.2.rpm
yum install iscan-data-1.15.0-1.noarch.rpm
yum install iscan-2.28.1-3.ltdl7.rpm

1. the scanner works only on a USB2 port, not on a USB3 port, why?

2. with xsane, I have access to the following resolutions only: 75,
150 300, 600, 1200, 2400, with scanimage: 75, 300, 1200, 2400.
Why is it not the same list?
How can I have access to more values as with the Windows tool where I
could select whatever value I wanted?

Frédéric