Your ballast resistance check from several posts back is too high. 0.5-0.6 ohms cold is the stock spec. But to make sure you are measuring it accurately; short the ohmmeter leads together and record how much resistance is just in the leads. Then measure the ballast cold and subtract out the lead resistance to get an accurate number.
The MSD 0.8 ohm ballast is the closest to stock. The best is an NOS ballast from eBay, PN 2095501.
Very glad your secondary stop screw adjustments helped. Don't be afraid to do it again; it can take several iterations to get it optimum. The exposed primary T slot is not normal so I suspect you need some more adjustments on that.
And I agree with AJ on the timing; no point in pushing up to detonation for a street car and if you are 2 degrees off, you are preeeetty close. Be aware that you can get temp and humidity days that will promote detonation more easily; cool, dry fall days act like lowering fuel octane by 3-4 points versus a hot humid day! So some margin is wise.