Let's start with aiown/aionios. Apparently, the "only Ancient Greek teacher" at his school hasn't sufficiently read the classics noor any of the papyri from Oxyrhincus o elsewhere. 'In the vernacular as well as in the classical Greek aionios never loses the sense of perpetuus."--Moulton and Milligan. If aion/aionios means ONLY "an age" then God Himself is mortal, since in 1 Peter 1:25 "The word of God remains unto the age (aiown)"
Baruch 4:8 "You have forgotten the everlasting (aiwonios) God."

As far as the lake of fire, the phrase used in the Apocalypse 20:10 is "eis tous aiqnas ton aionon. "unto the ages of the ages." This phrase is used repeqatedl throughout the Old and new Bible (in the Greek anyway)inrefernbce to God (Galatians 1:5; Phillipians 4:2 1 Timonty 1:17 2 Timothy 4:18Herbrews 13:21.
I also refer you to Sirach 18:1 "The Living One to the age (aion) created all things."
In 2 Peter 2:4 the writer uses the word "tartaroo (a contract verb) that is "to cats into tartaros," a place lower than Hades in which divine punishment was meted out according to both the Greeks and the Jewish apocalyptics (See Philo and Josephos)and which Job says "God holds captive" 41:24. Well before the first century A.D. the Jews saw Hell as a place of punishment. Our Lord does not contradict this.
Now, I'll post later the Orthodox view of the eterality of Hell