You're almost correct. The dynamic spine is the spine based on length of arrow,draw length, draw weight,and arrow component weight for an arrow when shot.

All arrows that are marked the same have the same static spine. i.e. 300 series etc. The static spine is measured using a weight and only gives the stiffness of the arrow when braced across 28".

However, for dynamic spine the a 28" arrow will have a stiffer dynamic spine than a 30" arrow due to it's shorter length. The same arrow with a 100 gr tip will have a stiffer spine than one with a 125 gr. An arrow with a wrap will have a stiffer spine. Any weight added to the rear will stiffen the dynamic spine. Any weight to the from will reduce the spine. The same length arrow shot out of a 30" DL bow will have a weaker spine than shot out of a 28" bow due to the longer power stroke.

What's an ideal arrow weight for hunting is different between a lot of people and opens up a big discussion. However, I can tell you how I choose my set-up and what I like. That doesn't mean it's perfect and there are a lot of ways to choose an arrow.

I decided on a broadhead weight and a draw weight that I expect to be using for hunting. I then used a program like OT2 to narrow my arrow choices down based on an arrow length that I want to use. That actually got me to an arrow that is spined a little stiff (which is recommended for hunting). If the shaft were a little weak I'd add a wrap (which I'm doing) and possibly shorten the shaft if needed. If I needed to I could also go down in draw weight to get the spine a little stiff.

My finished arrow is around 420 grains. a 27" GT XT Hunter 7595 with a 125 grain tip and wraps.

There are guys on here with a ton of experience that can explain it better if I screwed up or missed something.