First, I'm also a musician using my Hackintosh in my studio. It would be helpful for me to make contact? PM me? More on that at 11...
Now, for something relevant to your problem. I've got GA-Z68A-D3H-B3 Motherboard & am running Snow Leopard I was able to run Multibeast & use Realtek Gigabit Ethernet 2.0.6 as my Network & it worked for me.
Next, I had boot0 error problems & couldn't boot from my HDD & had to use iBoot for quite a while. One thing I noticed was that while booting from iBoot, I was only running in 32-bit mode. SL would not go into 64-bit mode & therefore would only see 4GB of RAM. I would assume that's why YOUR RAM values are wrong. You're only running in 32-bit mode & it can only see 4GB of RAM, right? That said, I would bet that there are many other "side effects" of booting from iBoot. Once I used MacMan's super-secret dd command to copy the boot block from another SL system, I was good to go & could boot into 64-bit mode. Once you're able to boot from the HDD, I would guess many things will work differently. They did for me.
Is it possible that you're getting a boot0 error & that's the cause of you not being able to boot from your Hard drive? If so, check out MacMan's Golden Thread on "boot0 error" & see how to copy the boot block from another HDD & at least you'll be one step closer to getting things to work.
Good luck & happy Jammin'...
Now for something completely different... WHAT is the time out setting on this forum now??? Every time I write something more than 2 lines, I'm timed out!!