Exactly: It means that you don't have a realtime kernel. He said it is not good... but with a lowlatency one is not so bad (In my opinion, is better to have a lowlatency one those days, expecially on a laptop).
-Kernel with Real-Time Preemption... not found
To enable the tickless function I think you have to recompile the kernel with appropriate options (and maybe it is possible only for realtime kernels)... I never done it and I think is not necessary for a (very) acceptable setup.
-Checking kernel support for tickless timer... not found
I never fed the script with my soundcard's IRQ. Basically because my laptop's BIOS doesn't let me to modify IRQs, so change things could be too much tricky.
I think that your setup should be good, all the "not good" and "Warning" you see are the same I left "unsolved" on my machines, and they works very good.
Have a look at your BIOS settings if you think you have to handle IRQs (remember to carefully change the BIOS settings, make sure to be able to restore the previous situation). In my case the solution was to kill all the other stuff that caused the interrupt to sound related processes, without handle IRQs settings (as i couldn't do it). Speaking about BIOS: maybe there is something you can disable in order to improve performances, as I made with my new desktop computer (in my case I had to disable my Ethernet controllers, not painful as I use wireless network, as the system was usually go mad searching for wired connections causing xruns).
All the ways I have to probe IRQs are the one I used in the thread I linked.
Looks so odd you have to deal with so much xruns with your powerful pc... Make sure that other things that use the USB bus are not interfering (webcams and/or other stuff could be disabled in order to test). Could you repost your computer full name model?