I'm a bit late, but I thought I'd just give you my two cents.

I'm a Christian as well, and pretty serious about my faith. Over the past few years gay marriage/abortion have been huge talking points here in Ireland, and this topic is inherently part of that discussion.

The Bible is not something on which we can reliably base a society. It's an unfortunate fact that Christianity is an incredibly fragmented religion; the Bible talks a lot about compassion and unification, but even within our faith we're very fragmented and uncompassionate. If we can't even come to a consensus ourselves, why should we then start forcing our beliefs down the throats of other people?

Your game analogy isn't entirely accurate. Simply by functioning in society you are including everyone else in your game; and there is no referee.

My philosophy is that we need to make a clear distinction between the "societal" teachings in the Bible, and the "spiritual" teachings in the Bible. The spiritual teachings are time-invariant and as applicable now as they ever were. The societal teachings are useful because they show us how times have changed and how people used to live. It's up to you to look at the world, look at the Bible, and come to a conclusion that makes sense to you.

The root of Jesus' teachings was the individual, and their relationship with God. When it comes to issues of society as a whole all you can do is think things through as objectively as possible, and then come to your own conclusion.

So to take it back to one of your examples, if I were a baker, should I be able to refuse to make a wedding cake for a gay couple?

In my opinion, yes I should be able to refuse to make a cake for a gay couple, but then I shouldn't be surprised when people start calling me an asshole and my sales dry up. As far as I can tell, it's a more "Christian" act to make the damn cake, and to celebrate and contribute to the joy and happiness of my fellow man.