Finally got some time to look into the DSDT issue, I had replaced the config.plist with the one similar to EDP bootpack and used the DSDT from the bootpack itself. Laptop booted fine without much issue after I removed the npci and PCIRootUID flags from the bootargs.
after applying some more patches for the brightness toggles, and sleep fixes, things are better working now.
Following are the list of items not working:
1. Bluetooth : Atheros 61xx chipset (0xE300 0x0CF3) might not work at all, as its not supported. It worked randomly some time earlier (couple of times to be exact), but not working now.
2. Lid changes : laptop does not go to sleep immediately after I close the lid. (this is working fine with DSDT in the EDP bootpack)
3. Built-in ethernet port is detected (Realtek 8111) but I don't get an IP address when I connect the cable, it always gets the self-assigned IP address, even though it detects that cable plugged in.
4. Sleep : even though it works, USB ports are not working, need some more time to experiment on this.
5. Shutdown / Restart: does not power down or restart automatically, I have to long press the power button to power off and then power on.
Anyhow, Thanks much Jake for the help. Hope I would be solving the remaining issues as well soon. If anyone has any pointers to solve the above issues, please let me know.