You can't move NPCs by events like that. One way I can think of is putting the Heart in a layer, hiding the layer, attaching it to a coin and making the coin move by events. The coin's death can spawn the Heart.
About the subspace, I think I improved it a little. See here:
Before and after:
https://www.mediafire.com/?masxgfcvhc8bq66
That's as close as I can get to the palette change in SMB2 without having to make an entirely new tileset for the Subspace and remaking the non-Subspace section from scratch.