For me, this is SO much better. A real improvement and something I'd certainly want to read.
I don't think you need the last words of the intro line.
First paragraph is almost perfect. I think there's a slight repetition - the 'more than he bargained for' and the 'it has not prepared him'. I'd also look at the moment when you switch from Angus finding the silver box to the effect it has; there's a slight jarring moment there that's something to do eith the 'Instantly...' which makes it seem as if a stage has been missed somehow. I think. I wonder if it needs more 'cause and effect' and an action on Angus's part to take us into the next sentence.
First half of the second paragraph is great as is, I think. It nicely lays out the result of Angus's action and the change that's made to him as well as the dilemma that results.
I think your doubts about the second half are fustified. This, and the third paragraph lack the focus that the first one has. Mentioning Hades by name at the end seems a little out of context here; I know he's your primary antagonist, but I wonder if you're better sticking to the generic 'gods' in the blurb?
The last tagline is almost there.
I'm going to be really cheeky and offer a quick (and still far from perfect) edit. I hope you don't mind, and feel free to ignore completely!
Ancient Gods still roam amongst us...
When visiting the archeological site of Culloden Battlefield in Scotland, former U.S. Marine Angus MacDonald finds a mysterious silver box. Opening it thrusts him into a world for which he is not prepared; a place where gods themselves walk in shadows and their influence touches every part of humanity’s existence.
Granted increased strength and enhanced senses by the power of the artefact, Angus now finds himself almost the equal of those the gods of old. Will his new-found abilities be enough to defeat the malevolence of the God of the Underworld? The Marines never taught him to fight deities, but he is all that stands between humanity and slavery.
Against him stand not just the gods but earthly powers, including a covert division of the Pentagon with their own sinister agenda. To lead the resistance he will need the help of friends and family. Most of all he will need to understand his own newly-acquired powers, and why he was chosen.
This page-turning thriller sets man against gods in a clash older than time. When the fate of the world rests on one young hero, who will pay the ultimate cost?