Is it true that the Imam's standing place for the Friday prayer must be level with his standing place on the minbar for delivering the sermon, so that he cannot stand in front of it or behind it?

The Imam's position on Friday for prayer has no relation to his position for the sermon in terms of alignment. There is no evidence that his position in prayer must match his position in the sermon, whether in terms of being further forward, further back, or in alignment. As for height, his place of prayer should be below the level of his sermon position, as the Prophet, peace and blessings be upon him, used to deliver the sermon from the pulpit and then descend to lead the people in prayer.