You have got to trust your instincts and then go over all of the details after the fact like you have.There is nothing more you could have done,hind sight is always 20/20.I can't possibly find any criticism,you have already dealt with what you would have done differently.
I have not yet established the ability to move tree's in to the spot that I want them to be.I like to hunt out of hemlocks for the back round cover that they provide,but some times I go into hardwoods because of the obvious,them being where I feel I need to be.If I had a gagger coming in directly at me from that distance with nothing between us I wouldn't have moved either.
Good luck to you! I hope you get another crack at him!