This shit drives me up the wall even more than "unalive"
You can't stop people saying slurs but an entire generation will subconsciously alter their entire vocabulary because they grew up on corporate platforms with very heavily moderated text chats and comment sections and they ended up internalising the filters 
Edit: I was not aware of the AAVE origins of "ahh" which pushes it more towards the territory of legit slang. Still, I stand by my general point about automated moderation influencing language being bad
A lot of us don't pronounce the -ss in ass so it sounds like a held ah-. If you know Japanese it's like the っ in a word like natsu vs nattsu. It sounds almost like a pause in a sentence. Depending on the sentence it may also sound like aa instead. Thing is, we don't really write it like that, at least up til my gen, idk bout these kids but it looks like a literal writing of the pronunciation. A similar thing is done with iono (don't think that one is very common though) which stands for I don't know and is based on the almost slurred together way it's said from dropping consonants in speech.
"I unno" isn't all that rare to see typed out
I'm familiar with the concept, but in my head I intuitively pronounced the a in "ahh" like car, not like cat
Oh, nah, I'm pretty sure it's both depending on the region. AAVE has regional differences and I think that pronunciation is one of them
I do think the a in car is more common though, mostly has to do with how the predominant regional accent influences your pronunciation is my guess, but I'm not a massive linguistics nerd so that's a fairly uneducated hypothesis
So there are places in the US where people pronounce ass like arse
I presume so. I've never heard the full word pronounciation, but I've definitely heard it with the dropped consonant, so I presume anyone in the region who says it with the consonant pronounce it that way. I'm actually lowkey losing it because I have no idea how I've heard one without the other...