8ba distributor questions

[GB SISSON]

My recently completed 276 8BA engine is running great and because of that we are planning some road trips. I am putting together a kit of spares which would be at least another distributor and carb. I have a few extra of each. This morning I cleaned up a nice 7RA distributor and started looking at points and condensors in my box of ignition parts. I am running a nippon-denso condensor from a toyota in my 276 now and found another in my landcruiser stash. So now I have the distributor in the vice and a good battery alongside with a napa 12 v coil with internal resistor and wired for negative ground. Tt easily throws a hot blue spark 1/2". Pretty loud snap too. But I noticed it arcs across the points as I rotate the gear. With a clean spark plug instead of the 1/2" gap it still arcs at the points, but way less. I tried other condensors, still the same. Then different points with no change. Lastly I tested a never installed NOS 7RA distributor with the same results. Having not worked on distributors out of the car much, I'm going to assume that this is normal and the condensor will do it's job keeping the points from pitting. Unless I'm missing something. I have a few more questions.
1) How do I remove the breaker plate for further cleaning and inspection?
2) On my installed 8BA the old vac unit advances the timing visibly (shown with my timing light) and with the hose in my mouth I can easily see the breaker plate moving with the cap off. It advances while steady suction but the suction has to be ongoing as it will not hold. The NOS vac unit and the napa unit both hold suction indefinately. I would ask the panel of experts, Which one of these two would you trust the most on my primary distributor? One is made overseas and one is unused but 70 years old. Thanks, GB