An excellent coin that needs professional cleaning. Your coin has BD and needs curing; see the circled below.
Hi. How hard is that darker stuff on the reverse, hard would make this a tough one to do unless you've done other similar ones!
What you take off could mean no patina under, or something even less attractive. The small poc marks look like they are within the substance, not on top of it.
I would agree with awl, in that its worth considering the price and scarcity of coin like this, lest you make a mistake you will regret (been there, greater than once).
I would leave the coin as is. The coin is already nice right now and it is best to not risk messing it up. If you do decide to clean it, practice mechanical cleaning on inexpensive coins beforehand.