As a Christian and a protestant (unmarried as yet, so I don't have personal experience but I'm still allowed an opinion, right?) I have a thing or two to say about this.
First, I think married couples who have intercourse should be prepared for the possibility of children. They need to be responsible and not be taken by surprise if something happens, regardless of the special precautions they take. That's just a given, and any Christian who would call a child a "mistake" clearly doesn't understand their own religion very well.
Secondly, why should sperm be given any special status? In your post, you say that you'd rather find other means of pleasuring your wife--which I understand. What I don't understand is why "every sperm is sacred," and why the man should be deprived of pleasure just because he contains one half of the genetic information necessary to create a human being. So what? Sperm is pretty much worthless in regards to procreation without an egg to attach itself to. Pleasure is as much a function of sex as procreation, and nothing tells us otherwise.
Third, yeah, the Bible's fairly silent on the issue of what's allowed sexually within marriage. Which leads me to believe nothing's really disallowed unless it fails to glorify that specific marriage. The Song of Solomon and other passages make it clear that the husband and wife should take pleasure in each other in whatever ways they deem most appropriate. To say something excluded from the Bible is automatically wrong is to make an incredible jump in logic. It's like the Christians who hate on metal because it's "inherently evil." What, did they confuse Plato's Republic for the Bible or something? I don't get it.
The more I study Catholicism, the more I'm intrigued by its bizarre dogmas, restrictions, and customs--some of which have entered the protestant church. While I have no problem with someone's personal decision to refrain from intercourse (actually, I respect chastity), as a doctrine it's just misguided and strange, mostly because of its lack of any Biblical foundation. And yeah, obviously most Christian principles will seem strange to non-Christians--that's fine--but at least you can trace them back to the supposedly holy text.
EDIT: Why on earth was "LOOK AT ME, I'M AN ATTENTION WHORE!!!!" in my post earlier? o.O I had to replace it with the word "post"...I don't know what I had there before, but it seems...unwarranted.