When it runs on the ignition is turned off so that has little effect.
A slower idle speed would probably help though.
I would go ahead and advance it to where it runs best and deal with the
running on separately.
I've had enough problems with SUs that I haven't gotten into Webers (nor have
I had the money but I can fix SUs).

I'm not sure that which oil you use is going to make enough difference that
you can tell it, although perhaps synthetic will. Your temp range is narrow
enough there that you should not have to go above 40 or below about 20 unless
you are running extremely hard (hundreds of miles of racing, etc)

The quieting you get from thicker oil may be at the expense of the fluidity
needed to get lube to tighter places. If your valve lash is adjusted right
it should not be too noisy. Better get that tailpipe fixed though. Breathing
that stuff isn't good and it also contributes to corrosion under your car.
--
George Downs, Bartlesville, Oklahoma, Central US