I'll take on all three and give you my personal take and then that of others I've engaged in heated debates with.
Take a look at this chart: 
Most non-religious people fall into the "some restrictions" and "no restrictions" category. In engaging with others, I've discovered that you can move the "no restrictions" to the "some restrictions" category. In particular, I use Gendercide as an example and point them to this website where they come away aghast.
My own personal position is that abortion has been legal for about 40 years. It is entrenched. Playing "all or none" hasn't worked. However, people can be moved to accept reasonable restrictions like the one I've shown above.
Non-religious people are big into civil liberties if nobody has noticed. That's why they have these groups.
My own personal take is that the extreme position that even involves letting the mother die is not one I can support. Put me in the Ann Coulter camp as regards abortion.
As for same-sex marriage, when you boil it all down and you talk to these folks, what they really care about are very simple things. Don't discriminate against the gays. If what they are doing doesn't harm anyone but themselves, let them be. Let them have someone in the hospital with them. Let them write a will and leave their worldly goods to their partner.
Basic civil rights and liberty stuff. Things everyone no matter who they are should have a right to.
Me? I support civil unions. I don't like redefining the word marriage. I'm the 30% minority of the non-religious, meaning I'm basically on YOUR SIDE in this matter.
You say that you are representative of a particular class of voters, but you’re not being clear about what your driving issues are.
I said I am part of that group. I did NOT say I am representative of the average non-religious person on the street. There is no such thing. This group is the same as every other group; you find all kinds. There are blacks, whites, asians, hispanics, males, females, liberals, and conservatives.
Its just that there tend to be more liberals in that group because they feel beset upon. There is truth in that and I can explain that in detail if you are willing to listen. I can even give examples of things I have had to deal with myself.
But, and this is for the record, don't assume that because someone does not practice a religion that they know nothing about it. I've written sermons for friends on the Greatest Commandment and the Golden Rule, both of which came from personal experience in having to teach that to Christians who have no clue that the Greatest Commandment has a prerequisite and the Golden Rule works faithfully in reverse.
If not, can you explain what issues cause your group to choose a Marxist who is trashing the economy and inviting increased Moslem terrorism over ... that other guy, who wasn’t quite so bad, economy-destruction-wise.
Since I voted a straight-R ticket, you've made an assumption about me that is unwarranted.
Primarily, people voted against Romney because of his gaffes, his throwing women under the bus with an extreme position against abortion - and let me add that taking such a position has now been a failure for 40 years - and throwing gays under the bus.
In short, trashing people and talking smack about them doesn't convince them to vote for your candidate. However, if you engage these people and treat them as people, you will be surprised.
I've gotten quite a few to back down off of an extreme liberal position and had them consider Barry Goldwater.
If they will consider Barry Goldwater, who makes Mitt Romney look like a flaming liberal, then what else can they be convinced of? Therein lies the challenge. I do this stuff on a daily basis. Goldwater is a hero of mine.