5th dnd – Questions about weight verification

During the last session, two members of my table tried to make a combo together!
I love when people contribute to the story especially if it's going to be something epic like this situation, but I need to learn how to handle this situation and make them happen. appropriate verifications, because I want them to continue.

-It was the situation.
"There was a great enemy, the Elven thief was about twenty meters away, and the dragon-hunter was between the thief and the enemy.The thief started running towards the fighter, the fighter held the shield taking a step that the thief could use to jump, the thief jumped using the hunting shield and hit the enemy in the face. "

What kind of verification should I do to see if this happens?
At the time, I did an acrobatics for the thief and I examined if> = 10
And constitution for the fighter and considered if> = 10

If the unauthorized weight is 90 pounds, how much STR or Con must a fighter get to support the unreliable weight?
1 by 10lb => 90lb = 9?

Same thing if this thief faints on the ground, what should the fighter do to know if he can wear it?

Until where can a character jump?
Until where can a character jump with this type of boost? (I think next time I will put a broken bridge on the map, they will try it)