Don,
It' s my experience that deer don' t leave " Pools" or " Puddles" of blood at the impact sight even with really good hits........they just don' t stick around long enough to allow blood to gather. I guess that' s where I' m confused.
It' s really hard to even guess what you may have hit, or if the sound you heard (crack) was the arrow hitting bone, or the tree, or even the arrow breaking.

To have as much blood as you are describing initially? The only hits I have seen that bleed THAT much are major blood vessel hits like the artery that runs below the spine area. That could explain the " Crack" noise, and that vessel will put out HUGE amounts of blood..........so will the femoral artery in the back leg. It' s amazing how much they will bleed if you hit these areas, and both can be associated with a crack against bone.

I don' t think shoulder blade, simply because its not typical to #1 blow right thru and into a tree........#2 They usually don' t bleed profusely, at least immediately.

I hate even giving these speculations because I too am assuming things I don' t know.......
I do know you hit SOMETHING major, and there should be sign.

If you are going the lantern route? Make a " Reflector" out of some tin foil.......wrap the back half of the globe so that it directs the light forward, and keeps it out of your eyes.
A cordless spotlight helps too. Dim lights stink. If you use battery power, have back-ups on hand.

Keep us posted.