The initial budget I heard back when it was first announced was $30-$40 million. Which would be an automatic death sentence (the pathetic Frozen overlay of Maelstrom cost a lot more than that). I wasn't given an exact final amount approved, just that it was "extremely healthy" (though not some absurd number like Cosmic Rewind's $500 mil). I was told the budget gradually and substantially increased multiple times during development to the point where it has strongly impressed the person I spoke with. Which is why I would make sure the details you have are current.
The budget alongside a lot of other new details this source learned after D23 last year made them do a complete 180 on their opinion of the retheme. Like went from saying it would be one of their worst rides ever and embarrass Splash, to literally "this is insanely impressive and should be a huge hit, a worthy replacement for Splash".
The comment I was told about the America Sings figures seemed to imply they would be reusing a lot of them. Didn't seem like just 7 or 8. That would be disappointing if that's the extent of them. I don't expect the Brer characters to appear of course.
Have you heard a ballpark number for how many AA's the ride will have in its entirety? I wasn't given a specific numbers myself, but the impression I got was that it would at least compare favorably to the quantity that Splash has, possibly get an increase. Which would be crazy given that Splash already has well over 50 figures (Disneyland has an additional dozen or so over WDW). Like I said, the two pieces of art that Disney released later last year looked quite well populated compared to the scenes they're replacing.
I hope you're wrong about the finale, because that sounds insanely disappointing. That room in Splash was an exceptionally themed space with a ton of physical depth and detail. And the sheer quantity of AA's made it feel very alive and dense. Trading all of that for 20 fewer AA's (I don't care how "impressive" the remaining 6 are) and a flat wall projection is nauseous to think about.