I felt like backwards seating was addressed by him saying "It wouldn't be comfortable". Equally, we know anything is possible. And during Swarm's construction, they explicitly said there would never be a backwards row, so it became a bit of a long-standing joke. So by not out right saying no, it covers the slim possibility it will happen.
As for Project Exodus being considered up to 500ft...
I'd imagine 500ft was sort of thrown around in a brainstorming sort of phase. Like:
"What if we wanted to build the WORLD'S tallest roller coaster?"
"Well, the tallest at the moment is 456ft. So we'd have to beat that...what if we went up to 500ft?"
"Saudi Arabia are looking at building the tallest/fastest/longer coaster and that's going to be above 500ft"
"Hmmm yeah, this sounds a bit much"
Realistically I doubt they ever considered anything anywhere close to 500ft, but it's a cool number to throw around for the wider audience. Also, in terms of practicalities, it's just not.
I'd love to know what their early brainstorms were like though. I wouldn't be surprised if they did genuinely table ideas of "Tallest non-launched coaster in the world" (ie beating Fury 325) or "Europe's tallest hyper coaster" (ie: what Hyperion was marketed as at opening). The latter isn't too crazy to consider either: Hyperion is only 17ft taller.
Presumably, budget, space, engineering considerations, impact to the local area (noise) and more would be what stopped that happening.