HOF, sure. When you start talking about ATG the goalposts shift. No, I wouldn't consider him an ATG personally.
Depends on what you mean. He wouldn't scratch my top 20 ATG heavyweight list, but then neither would Fury or Usyk, and I am big on both those dudes!
AJ is well below ATG status. He's a decent top ten heavyweight contender, a former titleholder, but he's NOT a great fighter.
He's HOF worthy but shouldn't even be considered as an ATG. The only Heavyweight with ATG cemented status currently is Usyk, even Fury is questionable.
No, he isn't. Unfortunately he didn't really do enough. He was only champion because Fury retired and I think history will remember him as a stop gap who couldn't beat the very best.
As much as I LOVE Usyk, he's not got a deep enough resume at the weight to be talking about ATG at Heavyweight IMO. If he beats Fury then that makes a massive difference!
He wasn't an all-time great before the first Ruiz fight and his qualifications have only gotten worse since then. The answer is a definitive no.