Hi PRS,
I was sponsored by my husband too, so let me try to help.
My first question is will it matter that my name on the documents now is my current last name and not my married name being that I'm not married yet?
No, I don't think it does matter. Actually, I'm married too and I kept my maiden name. It has never been a problem for the CIC when we've done the paperwork.
Sorry I'm not American so can't help with the security clearance...
Just wanted to add that you don't have to be married to be sponsored. Sure, it's sometimes easier, but you could also fit in the "conjugal partner" category, as long as you can prove that for now, you can not live together (visa problems, studies etc.)