[Zero10]

You _should_ be safe for up to 2 teeth, but I have no idea how you could possibly go in 1/2 tooth increments.....
I'll give you some highly classified information, for best results, align everything with the timing marks. Advancing/retarding by 1 tooth or more is going to make things worse, not better.
There are adjustable cam gears out there, but for the most part they are there to restore timing when the head is milled a large amount.

Go test your compression tester on another engine, or try a leakdown test on your engine.
If it is cranking at 400-600RPM and sounds like a sewing machine then you have bent valves, but even then you should eventually get a backfire of some sort.