Not that easy to find, even the site I used to use didn't start tracking serve speeds until the FO 2003. Perhaps
@abmk might be able to find it from old box scores. It's not just the speed, Hewitt a way better returner than Thiem for example couldn't break break Aynaoui because of his placement and the way he mixed it up - Aynoaui was hitting some really great angles throughout, mixing in body serves, flat ones up the tee etc...there was a lot of variety to his serving that you're not accounting for. I hope we can at least agree that Roddick is the best server of the group...
As far as movement goes, I feel the same way about you. There's no way you can watch both matches and think their movement isn't even close - Thiem was a good athlete but he was never an elite mover the caliber of the Big 3/4, Hewitt, Monfils etc...young Roddick was very quick and his footwork into his backhand corner is very good here. He's pulls off loads of great gets throughout the match. To say it's not close is just insane to me...
Likewise don't see how you can say they're hitting way way bigger off the forehand, like if you just said bigger, fine I guess but way way bigger? No way. Like even in the two points you so lovingly picked out there's no way Djokovic is hitting his forehand bigger than Roddick on average there. Of course it's a tiny sample but Roddick hit twice the number of forehand winners, longer match and worse defence sure (though also a slower court) but to do that with a way way smaller FH? No chance.
What year did Djokovic play his best tennis in absolute terms in your opinion? Likewise for Nadal? Because what I'm seeing is that you saying the absolute level of tennis is at it's highest, so if Djokovic is posting career best numbers in slams he must be at his best right? Like, how much of shot does 2023 Djokovic have against 2011 Djokovic in your opinion?