1) If you're happy where you are with functionality, mosec, I wouldn't worry about tweaking dsdt.aml Hardware wise, you should be fine but you never know (this works with F7 BIOS rev for this board. I don't expect much if anything would have changed for the most recent Rev (10) but my philosophy is, its not broken, don't fix it...
2) I'm not 100% certain, but I think while my system sleeps just fine, the HDD's may not sleep independently, I'll have verify that later.
3) I think you'd still have to replace the AppleHDA.kext from the original base install (you could try looking into replacing that when you add OSXInstall.mpkg to the /Packages/ on the base system, but I think that would require a bit of heavy-handed Pacifist manipulation. Alternately, as soon as Lion goes to retail, I'm sure MrJanek and his band of merry OSX fans will be updating Kakewalk to automate the process.
4) I can patch a dsdt.aml with the tools that the community has available as can anyone with a couple hours of boredom. There are several good threads on that subject alone (I learned it all on this site!) The DSDT.aml provided for the 45T board was all done with guides from here and tools!