I think you should always dry hop. If you're worried about it being too bitter you could reduce your 60 min addition. You could probably up the late additions (15-0) if you want more flavor and aroma as well.
I tend to make my bittering addition fairly small and load up with 5 or 6oz of late additions.
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I'm curious about the 2 lbs of Vienna and 1 lb of Munich. That's the beauty of beer: each recipe is different. Since this is your first batch, I'll offer a couple of meager tips about dry-hopping:
1) Dry-hopping is only adding aroma; you won't get any additional bitterness or flavor from them.
2) I always wait until after fermentation to dry-hop. The yeast is going burp and fart like crazy during the first few days of fermentation, and you will lose a lot of the aroma if you dry-hop right away. This also pushes a layer of foam up (krausen), which leaves a ring of hop debris and other junk along the top of your fermenter. If you dry-hop, this the krausen will cause a lot of your hops to stick to that ring, again, defeating the purpose.