Vocabulary:
illum: Referring here to Cestius.
pratextatus: Wearing the toga praetexta, and therefore in this case below the age of majority. [OLD 1b]
supplicium: Either “an act performed to propitiate a deity” [OLD 2] or a punishment, specifically an execution [OLD 3]. In this case, it could very well be intended to invoke both of these meanings.
revocaverunt: Of course it can mean simply to summon someone back [OLD1], and as Cestius complains it is used in the context of the circus to mean a recall to the starting positions in a contested race [OLD 2]. Another interesting use is specifically to recall a defendant to court [OLD 1c]; the word is serving a number of purposes here.
carcere: Another versatile word, it can mean either prison [OLD 1], the starting gates of a chariot race [OLD 3] or, if we take exierat to indicate an escape, could be the Underworld [2b]. Whatever complaints Cestius has, it is clear that Quinctilius Varus at least offered a versatile phrasing that could be interpreted in a number of contextually appropriate ways.
novissime: The superlative of novus, “newest” and therefore “last.”
Grammar:
oculis: ablative of separation
quomodo: adverb meaning “like”
novisimme: last definition of novus and means “finally” or ” at last” contextually [L+S, II. Transf. B. 3. B]
Syntax: Cestius not only gets the last word here, but Seneca has a nice balanced sententia to sum up his criticism