Jam m'lovely, don't listen to what some people are saying, seems to be a lot of sniping on mn recently.
You're not unprepared at all, you've done everything right. I've had dogs throughout my life, we have one now even though I have a 9mo dd. Shock horror, not a dog, and a baby.......together!
Basically what you need to do when pup goes to bite you or A, is say NO and act hurt, and turn your back on him. This is the same reaction they get from their mothers when they do something wrong, the mother will turn away and ignore said pup, leaving pup feeling bad. They soon get the message, worked wonders on my dog.
Get chew toys - lots of them, though I'm sure you already have. You'll soon find his teeth in them. Don't feel like you have to seperate A and puppy, or they'll learn to resent each other and feel left out. Safety gates are great as you can keep baby and pup seperate, without walls being between them iykwim? They can still see, smell, touch, lick eachother etc. Have 5-10 minute play sessions with them where they're both together, so they can get used to eachother.
Dogs are fab and A will love him. Don't fret, I'm sure you're doing great x