Interestingly the biblke does not call the demoins. Thye are called evil spirits. It uses the same woird for spirit as for the holy spirit andputs what we trnslate evil in front of it.
I cannot see how they can be the spirits of men who have died in their lost condition since the lost are held in a place of torment according to the teaching the Lord gave on Abrahams bosom and the evil spirits seem to have the run of the earth. I would say they are fallen spirits (angles).
Interesting. Which version do you refer to that calls them evil spirits? Lukes accounts?
Here is what I see used for their description:
G1140
δαιμόνιον
daimonion
dahee-mon'-ee-on
Neuter of a derivative of G1142; a daemonic being; by extension a deity: - devil, god.
This is used 51 times within the NT in some 44 verses of Scripture (KJV) where they are referred to as "devils."
I haven't seen the definition to which you refer to, except within four places within the NT; Luke 7:21; 8:2; Acts 19:12, 13. These four passages are limited to the author Luke via Holy Spirit inspiration. It is interesting this is Lukes description, yet it is different in other passages. I wonder if this is his designation due to his being a physician? Or, are these different than the "daimonion"?
In the OT usage they seem to be referred to as a "malignant" being, "shade" or devils. Devils may be a bad term, as there is but one devil? But the whole concept and our understanding here seems to be limited by the limited Biblical revelation, and then some poor terminology on our part theologically.
I see your argument that dead souls are being reserved in torment and thus cannot be demons, yet Merrill F. Unger uses this same argument about fallen angels being reserved in darkness as an argument that demons then cannot be fallen angels, but something other. But perhaps our understanding of being reserved in darkness is incomplete, not meaning they cannot roam, but that they indeed are held into a certain inescapable realm to which they are reserved and can never escape fully, yet they still seem to be able to oppress and posses within this world.