How many minutes depends on your uploaded video size. Only the original video size counts, not the other resolution Microsoft provides. I downloaded one of my Teams Meetings and this are the value: width=1920; height=1080; datarate 1120kBit/s; audio= 56kBit/s.
Record deletion is a manual process now, there is no automatic retention or similar.
And it does not matter if you download the video once or multiple times, it is not deleted by Stream!
There is no way to stop sharing to meeting participants before the recording starts. When the recording is uploaded to Stream, you have to go and delete the additional permissions to other users, edit the video (trim in Stream or download, edit and reupload) and reassign.