Running great one day and next it stalls every time I hit the gas too hard

It probably wants more timing, as increasing initial timing by 4* has helped. It may not be the whole fix, but is part of it. What happened is this: the extra 4* allowed the engine to make a little more HP; not quite enough HP as you still have a slight stumble, but enough extra HP to almost carry the load.
Your story is another great example of how important initial/idle timing is to carb tuning & why timing needs to be dialled in FIRST before touching the carb.

In D. Vizard's Holley book, idle timing is mentioned numerous times. But this a book on carbs, right, not ign? Above is the answer.