I feel that I am often judged as "nice" and "safe" from the straight female population. Am I wrong? If I'm right, what can I do to change said perception?

Buy a motorcycle.

Hmm...

You have to cultivate some perception, however feigned, of a slight bit of menace. An almost imperceptible desire for violence.

I dunno. I find that lifting weights and putting on a bit of muscle makes me swagger a bit more. Could be testosterone or whatever, but you have to not quite give so much a shit without betraying your inherent niceness.

It's a tough juggling act.

a spine I have. I'm just a guy who doesn't want to be a douche to get some.