Since I'm the one who asked ChaosRob for a definition - I want to say thanks for giving a great and understandable description of SPD.

I understand exactly where you're coming from and I don't think it's fair to blame you for how you are and the fact you're limited in a so called 'normal relationship'.
If I were you, I wouldn't care what others think, as to why you don't have a special someone. If you do want to be involved with a woman, I think it would be fair to be upfront with your limitations, at the right time so you don't mislead anyone. I would concentrate on being friends 1st and if she's seems interested, you could educate her about SPD. I'm sure there is a nice person who would be willing to accept you as you are. I think it's important to become friends and when you're comfortable then explain.
In regards to the friend you were talking about I understand the practicality of what you have to offer her, but it's important to be upfront. Your intentions should be for yourself/her and not just to satisfy others judgment of you. Are you lonely and just want a friend?
There are all kinds of people in this world and as my mom used to say - "for every pot, there a cover". Don't think how others perceive you and do this for yourself and be honest with what you can offer. I have heard of SPD before I just wasn't familiar with the short form. You're an okay guy as far I've seen from your posts.