He has admitted - as now have you - that the he only knows it's God because God told him so. If Satan was in fact deceiving you into thinking he's God, that would be exactly the kind of thing he'd say - and you'd never know because it'd be Satan pretending to be God telling you he's God.
The Bible calls him "The Great Deceiver". What greater deception could there be?
None that I can think of.
While your assumption is certainly logical to a degree, it doesn't fit probable.
If there are two beings and one created the other, for the created being to overcome, dupe and completely lock out the Creator is possible, but not probable.
Particularly again if the Creator is more powerful than the created being.
Which is what the Bible claims.
Otherwise one would have to assume that the Creator would abandon our plight and allow the created being to perpetuate the deception.
However that would only serve to strengthen the created beings hold on us, which does not sound logical or probable.
Further one would have to assume that the Creator creates with no provision for contengencies of this magnitude.
That does not fit logical or probable either.
Under Omniscience, Omnipresence, and Omnipotent attributes it is not only illogical and improbable but impossible without consent.
To paraphrase the Bible "Can the pot say to the potter what will be what".
Likewise when two entities are at odds there is always identifying factors to differentiate between them and they exist somewhere.
Now in this case they are claimed to be in the spirit realm.
And we are born under the Satanic spiritual influence due to the fall of Adam and Eve.
And the only way out from under that influence is through a spiritual rebirth afforded through Jesus Christ.
Having accepted and recieved that,(Holy Spirit) it is unmistakable as to the perceptable conscious difference that, the presence of it provides. Among which is a witness to and revelation of the Bible and the spiritual realm.
And in opposition to all carnal sinful practices.
Now if it is a deception, it is certainly doing God a favor since it backs him up at every turn.
That being the case at least as far as Biblical perspective, it is in complete harmony with the logic presented there. So it is not based on God told me so, neither does it remove your free will choice or unduly influence it.
Thats the biggest reason for it being a non deception IMO.
You can choose to trust in and rely on it or not to.
However I would caution you that it is relational covenant, so somewhat like cheating on your wife, there may be some adverse consequences to ignoring it.
As I said, you would have to recieve it, to judge first hand if you think it is a deception.