Short question: How do I find out what my pitch is suppose to be?

I always thought thumb pitch is just a preference. More reverse pitch = thumb is easier to come out, more forward pitch = thumb hang in longer.

There used to be a formula pro shops used to determine pitch. I used to have a chart because I could not remember the pitches. But, then again, this chart wasn't exactly "modern". Even then, there are factors that transcend any "theory"; thumb flexibility, thumb length, and skin texture (dry or moist). You need to factor all three of these items into the equation, but even then, finding the proper pitch isn't always perfect the first time. Besides, people grow, hands change, bowlers evolve. All of these factors change the pitch over time.

Yea, there may be standard starting points or whatever, but unfortunately, it seems to be trial and error is the way.

Unfortunately, drilling is more of an art than it is a science. The better drillers get it "closer to right" than hacks do. Sometimes we luck out and it's a perfect fit, but sometimes we miss. When you have humans working with other humans and you are relying on the feedback from the person you're working with, sometimes communication breaks down. If a driller makes a mistake, I hope they're honest enough to own up to it and make it right. Some don't and that makes the rest of us look bad.

Does pitch help hold the ball more easily?

Yes. Proper pitch will allow the ball to stay on your hand throughout your approach without you having to squeeze the ball to hang onto it. A perfectly fitted ball will leave you with no pain in the fingers and no strain with your forearm muscles.

Some pro shops still use a chart, a modern one that takes into account thumb length and flexibility. It's a starting point that at least helps take the guess work out of where to start.

I had one of those charts, infernocal. It wasn't exactly modern, really. Most of the pitches were reverse and very steep at that.

This is the only chart I have seen http://www.jayhawkbowling.com/Pro_s_Corner/Pro_Shop_Forms/thumbangle.pdf, but it doesn't take into account short / long thumbs, sweaty / dry thumbs, nor how relaxed a perons grip is. According to the the chart I should have 1/8 reverse for my span, but I actually have 3/8 forward. That's why the fully adjustable measuring ball is so great...now if only they could make it durable enough to actually be thrown!