It's very true that to a new player it's not obvious at all what you're supposed to be doing. The reason I chose not to have the player spawn at the portal is because I wanted the player to "stumble across it" but that didn't work well with the 60 second limitation and also the freeze. It should have been 1 or the other.
The hearts were added very last minute, but yes, every 60 seconds you gain a new heart and to make it clear that it wasn't from an action ingame and confuse the player if a heart randomly appeared, I made the transition slow. I agree this is not well conveyed!
When you say a world indicator, what do you mean?