Several thoughts here....
First, congrats on the weight loss decision and I hope you reach your goal.
Venison IS leaner than beef and properly cooked, tastes the same. My brother and brother-in-law are hunters and excellent cooks. They would also NEVER shoot a deer in a manner that would make it suffer. I have heard (don't have proof though) that livestock in commercial slaughterhouses do not usually meet a quick merciful death.
Raw deal that your Grandma attempted trickery.
I wouldnt be able to go vegan, love meat WAY too much for that
to each his own.
Good luck to you