It's better to exchange tickets at 4, because the exchange counter only opens at 4:30 pm.
The best spot is indeed in the middle of the top of the amphitheater, but puanasee pwolll. Bring an extra beach cloth or umbrella, because you have to wait ± 1 hour until the show starts at 5:30 pm.
Yes, you have to bring extra sunscreen, an umbrella, a beach cloth, enough drinking water, a portable fan, because it's really hot like a trial in the mahsyar field 😭