Copy and paste of the OBD/old wikispace site are all Demonbane profiles here, literal.....LOL!
If I remember correctly, there are feats on the level of the island or beyond (Cthuluh, R'leyh undersea metropolis is the size of a continent, and the battles of Deus Machinas and what they can tank), before the great jump to Universal/Multiversal/more in Strange Eons.
By speed? In the past, the OBD believe that the Laser/Magic and Manipulation of the Light of Augustus and his Deus Machina was only Relativistic and not true Light, ignoring the principle and nature of Magic/Azathoth, which can change, manipulate laws, information, logic , reality, concepts, dualities, etc, each spell is a Universe in itself in terms of complexity (Start of chapter 3 this is explained to you) and more (this only in Zanma Taisei, where you leave novels and the sequel game?).
There are more examples of speed in Demonbane apart from the Light and more, how to perceive and move in a time stop, in a void, a places between Universes, traspass concepts like maneuvers (Winfield VS Titus, Kurou VS Titus on their mechas, Kurou dispelled Cthugha in their first battle against Tiberius, Kurou move at speed of light to dosge the bullets of Unaussprechlichen Kulten in Leica Route, Strange Eons what i you remember).
For the size of Arkham? there is no real mention in Demonbane about the size that I remember in Zanma, is based on his homonym in HP. Landcraft, each sector has a large square of kilometers in size, and the casual attacks of Nero / Nemeless One can do this in a west (Leica Route).
There is only data/information watered there (more in the novels) about the possibility size of Arkham and his sectors, so someone should collect them and try to make a cartography based on this information.
I dont know if in Kishin Hishou there are more feats, i dont know japanesse.