Yes S tools have a max level of 75.

I wouldn't bother putting to much materials into tools unless they are S rank. And A ranks I wouldn't go go past the level were you need silver ore and I wouldn't bother upgrading B rank past 20 or 25 but you can put how ever much essence you want into any of the ranks because when you recycle the tool you get back every point of essence you put into it and 60% of the ore and 0% of the coins.