Andy,
I think you are on the right track now looking at the guage and/or regulator, leaning towards the regulator. The BG 280 is more than enough on gas and if it is not leaking I don't see a problem even if you don't like their products. I don't think 2 in a row would do the same thing. I also think #8 or #6 is fine from the regulator to the carb, but downsizing probably won't make any difference toward your problem.
The thing that sticks out to me that it could be a guage/regulator problem is that you had 12lbs at idle and didn't blow the needle off of the seat. You should never get that much pressure drop. Where is your guage exactly?
Curtis