I urgently need you to check these few sentences. Thank you

1)Alonso is desperate because he thinks his son drowned. (I'm not sure whether it is a simple past of drown, or the past partiple, to be drowned?)
2) At the end Prospero and Antonio are reconciled/become reconciled (Which one is correct? I want to say that they made it up).

1. Correct as it is.

Yes, both the simple past and the past participle of "drown" are spelled the same: "drowned."

2. Comma needed. Either phrasing of the verb works fine. And here's another way to phrase it: By the end, Prospero and Antonio have become reconciled.

You can use either