I am usually around 2.5 myself, but I have heard of neapolitan pizzerias going up into the 3's. I move my salt percentage around a little depending on the kind of cheese I am using (grande is very salty compared to some others). Fresh mozzarella or buffala have very little salt. Dont add too much salt to your sauce. Romano ads a lot of salt too, so be careful if you use that. I think you can balance it out with the toppings and you will be fine.
Yes, salt does slow down the fermentation quite a bit, and in places without coolers for the dough (some old school spots in naples) they go up this high with the salt in the warm summer months. I have found that it can also make the dough tougher when it has this much salt.
Still, I think you will be fine if you let it fully ferment and be careful with toppings.