I think the C60 sub for C120 was a big part of the issue.. C120 has a pretty distinctive caramelly/toffee flavor to it that you won't get with C60. And it'll definitely darken the beer.
The hopping schedule in that recipe seems... well... weak. I don't know the calculated IBU from that off the top of my head, but I can see that not having a lot of hop flavor or aroma. If it were my beer (and it's not), I would target 68-70 IBU through a recipe calculator, move MOST of the hops to 20 minutes or less with a Columbus bittering charge at 60, and get at least 4 oz total hops in the boil. Maybe whatever you need at 60 minutes for the bittering, then equal parts Columbus/Simcoe at 20, 10, and 5 minutes. Or whatever floats your boat. I would get some Centennial in there, because I think I can taste it in the original. But maybe not, some hop combinations can certainly bring the same flavor profiles to the party.
Something else you can try is to have a 51K side-by-side with a 2-hearted. There are some pretty close 2-hearted recipes out there, so maybe have the two beers with a pen and notepad in hand, write down the differences you notice between the two, and bounce your recipe off a 2-hearted recipe with the differences in mind. For science!
Oh, and email the brewery. They're very supportive of homebrewing.