I don't have any experience at all with the Demon carbs so don't know what to tell you there other than Rupert has done all my alky carbs.
I agree with Hammer about the intake. I run the Super Vic and I think it's a great intake but might be just a tad big for a 460 with those heads. You might try a Victor Jr. with a carb adapter but that's probably close to the RM manifold you're looking at.
If you call Rupert he will tell you to forget about the EGT. He has told me examples of carbs he has put out that ran 1200+ in the 1/8 and he was fine with it. He thinks there are too many variables in the EGT systems and installations. He will tell you to jet it for best MPH and let the EGTs fall where they may. Still makes me nervous to see them up there though.
Are you running any kind of spacer under the carb? If so you may want to try it without the spacer.
What type of hood scoop are you using and are you running an air cleaner or a carb pan sealed to the scoop? If you're running an open front ram type scoop with no air cleaner or pan, the air flowing over the top of the carb can actually suck fuel out the top causing it to lean out and could cause the flutter you mentioned.
I run 10 AN line from the pump to the regulator and 8 AN to the carb.
Let us know how you make out.
George