Oh yea, and the front page of HN this time around.
It sounded like you got your hands wet in a lot of different things. That doesn't necessarily mean you are going to retire on this game, but think how many people are aware of you now and when you do Bullet Factory X (where you skeet-shoot puppies and elderly people) you'll have that much more information on how to promote the game or where to spend your time. It also sounds like you had a successful working relationship with your sister (as an artist) which is half the battle for any game title. So that's a big win right there for your next game too.
I'm not that surprised as the lack of feedback from bloggers though. I think I get 10 emails a day following the format:
OMG, Super Games Factory, LLC has just released the
most amazing game on the planet: Dish Washer!
Wash dishes in amazing stick-figure 3D! Contact us for
a free evaluation code!
Bullet Factory is a fun/simple concept, but it seems better as an ad-supported title (it's too simple) than a 99 cents title when you compare it along side other 99 cent titles I've seen in the app store. The bar is getting higher and higher and unless I see something amazing in screenshots or a trailer, it's not even worth the purchase barrier to entry for me to try it. Unrealized value (purchasing a game for 99 cents only to realize I hate the gameplay mechanics) is so frustrating to me, I'd rather just not buy something I'm on the fence about.
I would take the low-sales-since-december-even-though-you-are-marketing as an indicator that it isn't a high-demand game. Release a free ad-supported version of it "Bullet Factory FREE" and move on to your next title. Keep track of the download differences to learn a bit more about what worked, what didn't and where the bar is.
That's not to say your next game or the game after that won't hit -- keep pushing, you'll have a success and it will catch you by surprise.
They always do.