This is a very interesting plot.
It’s the type of “hard” science fiction that I like - but which is now dead. The big three authors were Isaac Asimov, Arthur C. Clarke, and Robert Heinlein.
The new-style elves, wizards, and magic swords don’t appeal to me - with respect.
AC&H set some unwritten rules. People can visit the past - but not the future. Visitors can only observe the current inhabitants - they cannot communicate nor interfere. They don’t have the power to change anything. The current inhabitants are not aware of visitors from the future.
If you wanted to adhere to these rules, the ending of your story would need to be modified.
Of course, anyone can change the rules. But I think AC&H arrived at their rules after a lot of silly mistakes, and complaints from snitty readers. They were highly polished practitioners after some initial difficult-to-see disastrous gaffes.
Here are some suggestions:
Michael can observe a conversation between Peter and a third party, who could well be the third-highest magician in the hierarchy - and therefore someone to be respected.
[In order to levitate (= rise or cause to rise and hover in the air), Peter must rise from the roof. In order to fall to his death, he needs to move sideways until he is no longer over the roof.]
Peter (to third party): "You can’t stop me from from performing my greatest magic trick ever.
Third party: You don’t understand. It will not work. You will fall to your death.
Peter: I know.
So maybe both Peter and the third-party were aware that levitation (which is only a trick) is only possible when above the roof - but as soon as the levitee is no longer over the roof - wheeee !!
Maybe Peter wanted some spectacular suicide ?? The reason would need to be hinted at earlier. His partner has switched to the third-party? Incurable painful cancer perhaps? Maybe caused by radiation from the tiny futuristic atomic plant needed for the levitation? These tiny plants are already established by Asimov in the “Foundation” series.)
Just a thought