Its normal for his age, what isnt normal is not having a mum and siblings to teach him manners! Its important you take as much of this role as possible so he gains abit of understanding about when to stop.
Iv got the exact same with my monster, shes nearing 6 months and has little respect for me and my mum who bottle fed her from a week or so old. I dread to think what she would be like if we hadnt tried anything to teach her!
First off no finger/hand play, use fishing rod toys or a shoe lace. If he bites and latches on dont squeal, going limp can work (but didnt for my monster). Blowing at their face can also break their attack.
One that was suggested to me was time out, being their substitute cat family means they like your attention so ignoring them isnt good