Hi Smoke Stack,
You may be over-thinking things; your wheels seem to be spinning really fast and you feel you're not getting to where you want to go.
I think if you have worries about being replaced by one of the other females, the first thing you should do is go to the male directly and ask him upfront if that is going to happen. You need to have a heart-to-heart with him. So you're worried about being the same age as one of the other gals, of being less skinny, of having less-than-perfect teeth (LOL, I can relate with you there, my teeth are something else), of being not as sexually active than perhaps you think you need to be? You should tell him that these are fears and insecurities that you have. It would give him a chance to give you some reassurance.
As for the gal you're attracted to, love unrequited is a hard thing, but we can't help who we're attracted to, and sometimes it's kind of random. Heck, maybe the female who you're not attracted to is attracted to you. Maybe she feels "rejected" or "unrequited," who knows? Attraction has so much to do with biological chemistry; the one thing you can really do something about is fostering a friendship. Just about anyone can be friends, even if they don't have that much in common -- as long as both people are willing to countenance the friendship. I would still try to do little things to reach out to the gal you're attracted to, but don't push yourself too far in that direction. Enjoy your already-existing friendship with the other gal. That's something to be cherished.
Love is always a risk, as it involves vulnerability. You have to be brave to make yourself vulnerable. Be brave, and give time a chance. Sometimes things get worked out, a little at a time.
And don't be too quick to dismiss yourself as being "not cut out for this." You may be stronger, braver, and more beautiful than you realize. Just concentrate on being yourself, and have faith that you're worthy of love, just as you are.
Love means never having to say, "Put down that meat cleaver!"