There is a really good book on this written by the late archbishop Athenagoras Cavadas, answers alot of the questions on what this Hades is etc:
The World Beyond the Grave: Or the After Life - Athenagoras Cavadas
Hades signifies the underground or the abyss, the word heaven means heights or elevations. Jesus said in my Father's house there are many mansions refering to heavens. Heaven and Hades are presented as polar opposites but probably more because of cultural usage. Certain times the terminology is interchangeable. Hades can just be a generic 'hereafter' and other times its meant as that place where souls go which is not heaven, etc. Likewise heaven is mostly where the throne of God is, but can be used as an expanse space where demons congregate.
Probably in pagan roman times gentiles would have only been familiar with gods residing in an elevated altitute (heaven)- off limits to mere mortals, for example the greeks gods were said to reside in the highest peak in greece of Mt Olympos. For the most part everyone else went to the underworld (where the souls had to cross the river styx with a guide which is why i said Hippolytus account is a christianized version of these myths).
The OT speaks of these multiple heavenly realms (see Deut 10.14, 2 Chron 6.18, 1 Kings 8.27)
In St Paul epistle the the Corinthians third heaven and paradise is one and the same (see 2 Cor 12.2-4). Paul also teaches that in the lower heavens the demons reside
in which you once walked according to the course of this world, according to the prince of the power of the air, the spirit who now works in the sons of disobedience. (Eph 2.2)
For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places.(Eph 6.12)
Metropolitan Hilarion has an essay online on this subject:
Bishop Hilarion Alfeyev: Christ the Conqueror of Hell » Theology and Spirituality » Articles in English » OrthodoxEurope.org