Yep, yep, yep. At 8 weeks it got rough, and then again when baby started to crawl, then cruise, etc.
Get thee the crayons or another "sitting" activity --something he loves that you never let him do, playdough, finger painting, etc.. Get him occupied, then nurse. But let him do something he LOVES that he never gets to do, that requires supervision without actual "involvement." Let him make a bit of a mess, ignore it, he will get better at it and the mess won't be as big soon enough.
My daughter made a lot of cards with stickers. We made cards for some really silly reasons, but it gave me time to nurse and she wasn't climbing on the furniture. I would literally spend 2 minutes getting her started and then I would go nurse.
Also, talk to him while he is doing it. Sit across the room, but engage him in a conversation.
A few other things, get a routine going. Your 8 week old will soon have a real sleep schedule, so start putting things in place, getting your new rhythm established. Think about what you need to do to keep both happy. I got my baby napping early, at 8:15, so he was up by 9:45 the latest, so we could go to the park, to playdates, etc. before coming home for an early lunch. I literally woke my baby up at the same time every day, and still do. Sleep is a habit, so I decided to figure out a schedule that worked for all of us, and my son literally got on it without even blinking! I was shocked at how easy it was. Second thing, find a way to spend alone time with your oldest one, even if it just means taking him shopping on the weekend while baby sleeps. Shower him with love and kisses (I got into the habit of saying to my oldest, "i need a hug for energy, can you charge me up so I can keep running?" She loved it! and it made her feel special, like a real mommy's helper. Third, give your oldest a few jobs. Have him start cleaning up his plates and things if he isn't already doing that. Have him set the table, etc. Direct his energy and jealous into activities that make him feel like mommy's big special boy.
It's hard, but hang in there. He will settle down soon enough. With the hitting, find something he loves and take it away. My daughter likes to hit and bite her brother. Since instituting a "withdrawal of special something," she has been much, much better. Our something is one of those new solar strands of lights that change color? She is obsessed with watching our neighbor's lights every evening, and when she engages in any physical behavior towards anyone, she doesn't get to see them.