I have heard of two different methods for figuring draw length. The first is wingspan minus 15, divided by 2. With your wingspan being 72'' that comes to 28.5'' draw length.

The second method is wingspan divided by 2 1/2. that comes to 28.8'' draw length.

I know this will get you close with a release, but as far as shooting with fingers goes, I'll have to let a finger shooter answer that.