Two concepts to run by you. First, manifold vacuum should always be highest at idle and will drop off under hard acceleration and heavy engine loads. The way your vacuum advance works, coming from a ported signal rather than a manifold signal, is that there will be no signal present at engine speeds below 800 rpms, but will begin to apply as more throttle is introduced. You've indicated a belief that your vacuum advance isn't functioning. If true, that could be why you're not detecting a any detonation ping, simply because your timing isn't advancing far enough to induce that condition. Your distributor does have a mechanical advance function that will advance your ignition timing at higher rpms whether or not a vacuum signal is present. First thing I'd be suspicious about from the description you've given is a manifold vacuum leak. My suggestion to you, invest in a low cost vacuum gauge that you can connect to a manifold vacuum source and take some readings. As an example, an unmodified engine in a proper state of tune and in good overall health will display a steady reading on a vacuum gauge of 19-21 inches/hg at idle from sea level to a thousand feet above. If you're interested in learning and applying some basic, old school engine tuning principles, you will want to have some basic tools at your disposal. A vacuum gauge, a timing light (you don't need the best one that money can buy) and a handheld, digital multi-meter with dwell angle and tachometer settings are invaluable diagnostic and tuning aids. I'd hold off on advancing your static timing any further until you properly address your vacuum advance situation and determine what your manifold vacuum is at a true curb idle speed (sub 800 rpms). Reason being is, you don't have any idea where your initial timing is set right now. It could be 8 degrees advance, it could be 18. You need to know more about what your engine is doing right now because you're kind of flying blind at this point.
