When the tree is blown up, it clearly falls in front of, and not on top of Gordon. Further, Gordon never falls off of his horse. Yet, when West goes to the tree from the other side, Gordon clearly emerges from right under the tree.
At 39:40, the falling blade is not long enough to cleanly split the stairway post.
Despite the "darkness" in the lives of some of the members alluded to by the Archduke they are all among the elite of that time except for Mr Stimson a gruff crude murderous outlaw hardly the type to achieve membership in such a group- at THAT time today it would obviously be quite different.
Mr. Pearse is introduced as "the leading heavyweight contender," however at the time boxing was illegal in the US. Additionally, the first heavyweight champion was "Gentleman Jim" Corbett in 1892.
There is never any explanation who the hooded men in the cellar of Grevely Manor are, or how they got there unseen by Grevely and his servants.