Kalam

[Angrboda]

"First efficient cause" and "ultimate effect" and "intermediate efficient causes" and "following in order"  all of which appear in the argument above implies a temporal chain structure.

It sounds that way to modern ears, because we tend to think of causal chains as temporal things. Aquinas is concerned with what is essentially prior. His vocabulary is more Aristotelian, so it sounds unfamiliar to modern people.

Yes, because causation is temporal. It's an analytic truth of Aquinas' statement that he's referring to temporal succession as all succession involving causes is temporal. If you want to argue that there can be causal sequences that are not temporal, the burden is on you to show that such is possible. Until you do, your claim that Aquinas was not speaking of a temporal series fails. It has absolutely dick to do with Thomism and Aristotle.