Well, first off let me ask you why you're unhappy with the USB 1.1 output? Are you having actual problems (for example driver issues) or is it just because USB 2 is "better"? I ask because the limitations of USB 1.1 are just in terms of throughput, not sound quality, and for a single stereo output from the mixer, USB1.1 should be plenty.
If it's driver issues etc. I'd suggest a phone call to A&H's customer service department. In the UK at least they are a very helpful mob--I've heard tell that it can be best to Skype the UK number rather than mess around with the American one. (And if you're not in the USA, apologies--but the majority of members are!)
If, for whatever reason, you want to run from the mixer to the Scarlett, just go from the line out on the mixer to the line ins on
the Scarlett (the TRS sockets in the middle of the front panel XLRs.
Normally I'd say you'd have better quality going straight into your 2i2 with your keyboard--but the A&H is better than most entry level mixers and (though I've never compared them side by side) my guess is the A&H electronics are on a par with the Focusrite--so you'd lose nothing through the convenience of using the mixer as a routing device.
As for a book, I don't know of any that can give step by step specifics, if only because every system is just so different. However, one that I've recommended in the past is
AUDIO MADE EASY (OR HOW TO BE A SOUND ENGINEER WITHOUT REALLY TRYING) BY IRA WHITE. It's full of all sorts of good background info on levels, cabling, connections etc. and, though kept simple. all the info is accurate.
Hope this helps.