Forget factory specs when you've made changes to other things - they're meaningless. Don't let the specs play mind games with you and make you feel like you must be "wrong" because your car is different.
You're doing fine. First order of business is to find out how much total at WOT your engine likes, and at 34 degrees it sounds like you're probably right on the money. Most engines usually LIKE a lot of advance at idle no-load conditions, but as they move off of idle and start to see some load, not as much. That's one of the functions of the vacuum advance mechanism that a lot of people don't realize. At idle/no load your engine is making lots of vacuum so the diaphragm is adding a lot of advance. However, as soon as you add throttle/load and vacuum starts to drop, it has the effect of actually pulling advance OUT of the engine which is exactly what needs to happen under those conditions in order to stay out of detonation. Then as RPM increases, the mechanical advance starts to add it back in.
As long as it's not hard to start, doesn't overheat, runs like a healthy Pontiac should, and doesn't ping/rattle under load - you're fine. Don't sweat it.