A question regarding grasshopper's ability:

AH, BUT I'M THE SECRET BROTHER OF THE SECRET CRUSH OF THE FIRST GRASSHOPPER!: When Grasshopper is KO'd if no other friendly characters have been KO'd, after actions resolve you may place him on the map in your starting area on click #1.

If I play 9 grasshoppers in a 300 point game and no other characters will they all continually come back, will the first one come back repeatedly until a second grasshopper is killed, or will one of them come back once and then they all die normally?

Also want to make sure since it does not specifically say so (like fast forces solomon grundy) my opponent will not score points for each time they kill grasshopper.

They will score points each time because it says "When Grasshopper is KO'd" not "When would be KO'd".

After your first Grasshopper is killed and comes back, no other Grasshopper may come back.

With the use of other I would think at a minimum if I had one grasshopper who was killed brought back and killed again he would come back a second time as long as no other figures are killed.

Yes, the first Grasshopper to die would be the only one who could come back. And as long as no other friendly has died, he can keep coming back.