how good is his resistance since Diablo's time-stop can even affect someone who resisted another timestop(basically 2x layer),
Well, first, angels/demons naturally resist time stop while the Black Abyss's
time-bending is said to be able to trap even those,
should they go near enough. Satan's Augoeides is a beast that literally lol and broke said abyss from the center, even in its physical state.
Second, spirit (and soul) itself is unbound by time construct so layered time manip isn't really going to work, just like how layered fate/causal hax can't bypass acau 4 without feats. Even if we take the low-ball, the spirit/astral body, which is a more fundamental component than the physical body (and can work independently from it), is free of the material plane's temporal stuff which includes Black Abyss's which is time stop on Diablo's level.
Diablo have interdimensional range teleportation as he can go to the spiritual world and back to the semi-material world, so after realising that, Diablo probably will try to teleport there and do something that would work, idk
Dispel bounds still gg. More importantly, it would take Diablo some time to locate Astral Plane, given that he knows it is a thing first.
and if Satan still can move, the time stop also grant 1 million speed amp so Diablo have the superiority in speed, not to mention in base he have 10 million reaction speed amp that can make him use something before Satan can do anything
The point is how in-character, or how long would it take him to start using that. You did mention useful stuff, however, they aren't going to happen all at the same time, are they? Like while Diablo going through all of the steps needed, one attack from Satan would probably end the fight (due to EE that eclipses Diablo both in layers and the level of the erasure itself). And even
if Diablo gets the chance to set up his preferable situation, a single mistake, even as small as getting too close to Satan, would be fatal FRA.
I also want to point out that Diablo probably doesn't have anything to deal with AE1 Concept type 1 based and High-godly regen stuff, so this is an icon at best.