Re: I don't know what is 'normal' nursing behaviour...
Your LO's nursing behavior is normal for such a young toddler. As a toddler's independence grows, he's going to feel the need to check in with mom in order to feel reassured and confident. And checking in, for a nursing toddler, means a hug, a cuddle, and nursing! There's no need to put limits on his public nursing unless YOU are uncomfortable with it, and it sounds like you're not!
I feel that confidence is a nursing mom's best friend, so I would simply continue to nurse proudly in public. If your friends give you tragic looks, just smile broadly and say "I just LOVE how he still runs to me for nursing. These little 'touch base' sessions are so funny and cute. And they definitely help him feel more confident and independent."
When it comes to your husband, I would tell him that his opinion on nursing a toddler will be relevant when he himself has nursed a toddler. He may be embarrassed, but you're not. What you do with your body in public is your problem, not his. If he quibbles, you can explain that nursing is not just about nutrition. It's a mothering tool, and mothering through nursing allows you to have a calmer and more confident toddler. What's wrong with that?
When you feel the need for limits, you'll find a way to impose them, and imposing them/communicating them will be a lot easier when your child's language skills improve. I personally didn't put any limits on public nursing until my kids were into the 18-24 month age range.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"