I think that the best interpretation of Simon is the one that doesn't care anymore, but not in a pessimit way, but because he thinks he is already dead so he can take all with ease. It is almost as he was high.
I woke up in a place that is not the blood ocean and is pretty nice? I must be in heaven, I won my redemption, nice.
A beautiful angel looking after me? And it is just my type? Lucky me.
Another more weird looking angel that is a singing rock? I will not question how angels work, they are angels.
Are the angels giving a lot of information that seems to explain what happened to the whole universe and somehow they save it? They are angels, of course they know this kind of stuff, duh.
I can stay here as long as I want? I'm staying forever, jaja, I will not reincarnated, oh no sir, I'm staying with the pretty angel for all eternity, thank you.
There are threes and stars and planets? Yep, I'm super dead, but well at least is nice.
Like at some point his mind finally connects the dots, maybe Rocky makes a comment, maybe something breaks the illusion, maybe Grace confess his feelings for him and it is then that Simon realizes that he is not dead, and then all the ashameful things he had been doing -because he thought he did not have to care about something as little as shyness or shame in heaven- come to his mind:
Taking his shirt off whenever he feel like it, because nudity must not be that big of a deal for angels, right?
Just saying any thought he had in his mind out loud: Beautiful angel has pretty eyes, he said it, the rock-angel sing nicely, he say it, he feel like a little bug, he say it, he wanted to know how the pretty angel hair felt, he say it, etc, etc.
Those silly songs he had been singing narrating what he was doing when he was boring.
He naming all the threes and talking to them openly.
Letting the pebbles (who he thought were young angels not ready to angelize) do whatever they wanted to do with his hair, braids, ponytails, bows and just keep it like that the whole day.
He wished someone kill him so he would not have to face the shame of knowing he had been doing all that in front of Rocky and Grace.