How would Wally interact with an autistic child if he's there special interest? And what's more, are there any adult who treats the puppets well?
The puppets meet a variety of children at their meet-and-greets, but Wally is especially ready for all scenarios 
He’s ready for anything
He’s trained himself to be the most open and welcoming figure kids can look up to (figuratively) he’s basically fluent in asl
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He’s not fluent in any , but he knows a few languages which includes Spanish, French, Italian, Mandarin Chinese, Japanese, and a few more he’s especially not good at.
Worth noting, he studies Child Development to help write the best educational and entertaining episodes they can
I forgot to answer the second question, but yeah of course there’s adults who treat puppets equally, not everyone can be a horrible person. It’s the majority of big industries that are still assholes, and some small groups of bigots will always exist . That’s the way humans are
We all have accepted that one of the Denholm Brothers will die during Pirates.
Take my reasons on why it will be Scott.
During the beginning of Chapter two Scott was one of the last people out along with Ros. This was because Ros' backpack fed her Rotten flesh which made her unable to move. Scott was one of the last behind because he helped Ros by dragging her (or) waited for Ros to be able to move again (Needs criticism cause i forgot which one it was). This clearly shows Scott's willingness to put himself in danger to help another person. This is with someone Scott has known for only a month(?) so it's safe to assume he would do it for someone he's known practicly his whole life. During streams, Acho is shown to be very reckless and completely unaware of Danger. An example of this is during the events of "Below the Surface" star was very quick to offer himself up to go investigate the whirlpool without considering the dangers which could (and did) end up happening. It doesn't seem unlikely for Acho to end up getting themselves caught up in a deadly situation.
If Acho would be the one to die, yes there would be amazing angst and lore for Scott, it would be some what expected. Scott watches star perish, he becomes sad and angry, then he wants revenge. This is very clear because Scott still shows strong and loving emotions to Acho. He goes and actually expresses them. Where as with Acho, star doesn't show alot emotions towards Scott (or many things in general), he still loves his older brother, but struggles/doesn't know how to express it. If Scott where to be the one to die, Achos emotions would be unexpected, thus creating amazing and possibly unpredictable angst.
My final point would be their parents reactions. With Cleo and Water being the only other herons (not counting npcs) who were around before the Factioning, they'd be the most likely ones to inform Aurelia and Hudson. But, they both know Acho is related to Scott, so they _might_ make star tell their parents (which would also be a good way for even more angst may I add). But even if Acho isn't the one to tell them, they'd most likely make a big deal on how their "child has died" (possibly saying only if they're still unaware of Achos life). If it where acho who died there probably wouldn't be as painful angst. Yes it would supply a fucking amazing character arc for Scott.
Also the reason I brought up angst levels alot is because oh my fucking god Scott and Acho have angsty characters outside of Pirates as well as in pirates.