I can assure you that Bro. William Chalfant has done PLENTY of background check into his assertions. He holds at least one PHD, and has been a student of early church history since the 70's. I know him personally and have had several conversations with him concerning early church history. Also, Thomas Weiser is an outstanding student of early church history. I am not certain about his formal education, but his writing and scholarship is impeccable.
I am not certain that your assertion that he "was an occult member that talked to demons and angels" can be substantiated with this resource. And can your resource be trusted to be unbiased? Or perhaps it is another trinitarian or Roman Catholic biased historian that took personal attacks at him instead of grappling with the substance of his theology. I don't know whether your resource here can even be considered to be conclusive.
Also, even if this accusation against Swedenborg is true, doesn't necessarily bring the veracity of the monarch (oneness) of God into question. the fact that he held to one God (even the devils believe in ONE GOD and tremble -
Jam. 2:19), simply means that there were monarchian believers present during his time in history. He didn't stumble upon this by himself, seeing as the timeline that I posted shows that from the 1st centurty all the way down to the 20th century, there were oneness believers SOMEWHERE in the world.
Also, if ever goofball that professes to have the truth is put up as the poster boy for a doctrine, then we can do the same with the trinity doctrine. For instance, the fully developed trinity doctrine is the progeny of the Roman Catholic church. Now if we take into account all the doctrines of the roman catholics, i.e. Mary worship, saint worship, infant baptism, purgatory, indulgences, sprinkle baptism... etc., and then you take into account the nefarious history of that doctrinal system, it would seem to indicate that ALL their doctrine should be thrown out... ESPECIALLY THE TRINITY. So you want to bring into question one "oneness" individual who "may" have had a checkered past in order to bring into quesiton the veracity of his doctrine, but you reject doing the same thing with your doctrine. I suggest you come at this from an objective perspective, and examine the implications that in fact that there were oneness believers throughout history, instead of disparaging the historicity of this well established fact.