You're getting posts that you don't agree with and you're getting upset? That's just what happens when you post forums.
It sounds like you've tried your personal hardest and that's all you can do. Unfortunatley it's not enough for the pup.
You either need to engage the pup in a professional training sessions or tske him to a shelter.
Try not to be so hard on yourself. You've got to put your emotions to one side for a minute and think about how the dog is feeling; confused, scared, anxious maybe?
You say he's biting your LO but its unclear under what circumstance; is he play biting like you suggest, or is it agression? They're two very different things and both need to be nipped in the bud right now.
I'd keep him away from the LO, if he is around your LO then he needs to be constantly supervised; kids can be full on when dogs don't actually want the attention, but they will usually avoid biting and move away or growl first as a warning.
From what I've read, it sounds like you've not done anything particularly Pro active to stop him or deter him from the completely normal behaviour of play biting. (Every single puppy does this, and has to learn that it's not acceptable) he learns that from his owners.
We had to re home a fabulous dog, nothing wrong with her. Had her from a pup, had her spayed. She just deserved a life we couldn't give her. (She was a collie x lab) she was high energy, loving, caring, amazing. No vices. But still we made the decision that was within the best interests of the dog and she is happy with her new family now. They've done so much more than we ever could and she's come on leaps and bounds. (We do have another, older dog) but sometimes you've just got to give them up, whether you had the intention to or not.
Really hope you get something sorted before it's too late.