I'm obviously not a medical professional but it's my understanding the tissue of the corpus cavernosum is sponge like and saturated with blood even when flaccid thereby making it easy to draw blood from it. That seems to be the case from my experiments. However, I don't generally aspirate as I don't see the need.
Yeah, that might be the case. I know the human body above the shoulders, is very vascular.. which is why we bleed so bad when we cut ourselves shaving. I guess the genital area could also very vascular. The only reason I mentioned it is if you get that stuff in a vein, it's gunna hurt.