I would not eliminate the candi syurp. The extra caramunich is going to add unfermentables. The candi syrup is fermentable, so removing it would result in a higher final gravity and more sweetness.
In looking over Jamil's recipe, he mentions mashing low and long. I think that's going to be the key to countering the potentially higher FG and residual sweetness added by the extra caramunich. If you can mash at 148-149° for a full 90 minutes that will give you a more fermentable wort. The other factor is going to be a big pitch of healthy yeast. Definitely make a starter. I'd go with a 2L or even 3L starter. Either let it ferment out completely and decant the spent beer prior to pitching or pitch the whole thing 12-24 hours after making it.
Another idea would be to remove a pound of the mixed grains from the bill and replace them with table sugar. That would replace some of the unfermentables with something that is going to ferment out completely, perhaps balancing out the added caramunich.
Even if you do nothing, all that is going to happen is that the beer will be darker and slightly sweeter. It most likely will still be within style guidelines, if that matters to you, and will still be a darn good beer.
Good luck!
Chad