After he had killed the Egyptian, Exo 2:15. Not in the general exodus. The historical order of events is preserved: the flight to Midian, the Passover, the Exodus, the passage of the Red Sea.
The wrath (τὸν θυμὸν)
Only here in Hebrews. See on Joh 3:36.
He endured (ἐκαρτέρησεν)
N.T.o. Occasionally in lxx. Often in Class. He was stanch and steadfast.
As seeing him who is invisible (τὸν ἀόρατον ὡς ὁρῶν)
Since he saw, etc. The emphasis is on invisible, pointing back to the introductory definition of faith. The word is used of God, Col 1:15; 1Ti 1:17.