Learn English – Is “like so” correct

I think the English (as written) is a bit ambiguous. It could be an ellipsis, as you wrote:

The boy who lived (has now) come to die.

or it could be a command

The boy who lived. Come (here), to die!

The tone of the speaker would probably make it clear. I feel that the if the speaker was speaking in the first case, the word "come" would probably be spoken more softly, whereas in the second case, "Come!" is a command and would be spoken more forcefully.

The trailer is here and it sounds to me like it's an observation than a command, so I think the first interpretation is correct.

The phrase sleep like a top appears in The Two Noble Kinsmen by John Fletcher and William Shakespeare, which was first performed in 1613–14, and published in 1634.

There is a possible clue to the etymology in The Countesse of Pembrokes Arcadia, Volume 2 (somewhere between 1580 and the author's death in 1586) By Sir Philip Sidney, in which the phrase like a toppe is used to express the stationary nature of a top, which can only be moved by whipping it.

Griefe onely makes his wretched state to see
(Even like a toppe which nought but whipping moves)

From this, I believe it might be possible that it is the stationary nature of a top, which requires whipping to move, or wake, it that gives rise to the phrase sleep like a top.