In fact, the lake of fire is said to represent the second death (indicating that the lake of fire is symbolic).
I do not know if your conclusion can be safely drawn. Scripture says about the lake of fire: "this is the second death, the lake of fire." The text does not say that the lake of fire is symbolic, though that may be the case. Nor does it say that it merely represents the second death. It says that the lake of fire is the second death. This may mean that the lake of fire as an experience is the second death. To be in the lake of fire is to experience the second death.
Admittedly, the actual wording of verses like Rev. 21:8 is as follows: hO ESTIN hO QANATOS hO DEUTEROS (Cf. Rev. 20:14b). But ESTIN can carry the meaning "represents" or "signifies" as it does elsewhere in Scripture (Matt. 13:38). In fact, the very first passage found in Revelation indicates that the book is filled with symbolisms. As John reports: KAI ESHMANEN APOSTEILAS DIA TOU AGGELOU AUTOU TWi DOULWi AUTOU IWANNHi.
The verb SHMAINEIN can mean "to indicate clearly" (Louw-Nida) or more likely in this context, it conveys the thought, 'to communicate a message that is enigmatic in nature and difficult to interpret' (Aune, Revelation, Volume 52A:15). So ESTIN in Rev. 21:8 could mean "represents." Therefore, based on Rev. 1:1, the lake of fire may very well be symbolic. In view of other Scriptures concerning the eschaton, it would be fitting if the lake of fire served as a symbol of everlasting annihilation (2 Thess. 1:9).
Furthermore, death and hell are cast into the lake of fire along with Satan and the wild beast and the false prophet (Rev. 20:13-15). Do you think that death and hell and Satan and the wild beast and the false prophet will literally be tormented day and night for all eternity in the lake of fire?
When Scripture says that death and hades are thrown into the lake of fire, the meaning is difficult to grasp. It seems to be saying that there will be no more death and hades, since their conditions will be supplanted by the lake of fire. Yes, I think that Satan, the beast, the false prophet, and those who are thrown into the lake of fire will be tormented day and night for all eternity.
I think you rightly admit that abstractions like death and places such as hades cannot be tormented or experience the second death in a literal way. Why, then, do you think that Satan or the beast (evidently a symbolic creature) or the "false prophet" (another symbolic entity) will undergo literal toments in an everlasting fire? Heb. 2:14, 15 indicates that the Devil will be annihilated or brought to nothing? How do you understand or interpret 2:14, 15?