I think you should have the baby because you are doing it for the right reasons, along with the hope that it would be good for your SA as well. You say you are loving and caring and have a lot to offer, so clearly your maternal instincts are alive and that's the best preparation to have when becoming a parent.
I wouldn't say that having a baby would necessarily cure your SA. What it does is provide more opportunities to meet people in events to attend and things to do, and people you have to meet that are related to being a parent. Also it takes the focus off you - the more baby takes your time and energy, the less free time you have to ruminate and think negatively about your own life. Also there's always a companion, and you learn to appreciate the world through innocent eyes. It's quite refreshing and touching really. I admit that I sometimes cry just watching my little one. You will also grow alongside your baby and learn more things about yourself. I don't believe a person can be complete unless they become a parent. It does have challenges though but then life shouldn't be easy breezy.
I surprised everyone, including family, mental health professionals, and myself, when I managed to be quite good at mothering, despite lack of emotional maturity, selflessness, and ability to love and care for others at the outset. I also lack common sense, so it's being a very steep learning curve. I don't do mother baby groups and haven't a friend to meet up, not even family (due to distance) and would like some social contact, but i'm ok with it at the moment.
My advice would be to get as much sleep and naps you can squeeze out of a day, and to notice your mood changes and talk to people if you need to vent and be aware of post natal depression. Also whenever you feel moody or upset at something that triggers your anxiety and/or bad emotions and thoughts, try not to let it show infront of your child. But it's important to talk to someone adult about it when you need to. Children are very receptive and pick up feelings and behaviours easily. Make your child know unreservedly that their needs come first, even if you have to put on a brave face. I've seen some down right nasty and incompetent parents who don't have social anxiety, and I think somebody with the knowledge brought to the table by a mental disorder will be more prepared to cater to the psychological needs of a child.