I would not add late hops if you are putting juniper and spruce in there, personally. The "cloying" is going to be a product of the grain bill, mash profile, and the fermentation, not really the spicing you use. Well...except I suppose you could overdo it on the cardamom. My advice, if you have never made a spiced beer before, is to go way less than you think you ought to. You can always add more, but you can't remove it once you've added it, and you'll find that some spices can be overwhelming.
On another note, where are you getting spruce essence? I have been looking for sources of spruce tips/essence for a while to make a gruit, and so far have not been successful.
One other thing: 1/2 lb of molasses can be a lot depending upon the molasses you use. I added that much in a RIS I made a few years ago, and to this day it is by far the dominant flavor in the beer. Not that it's a bad thing, necessarily. People actually like it, but it is not nearly as balanced as it ought to be IMO. That is another one that I would add a little at a time to taste, because it's very easy to go overboard.