2. It does claim that God is one. It also claims that God is three. One essence in three persons--the Triunity.
3. The Bible repeatedly and emphatically claims there are indeed demons.
This seems to be a matter of deep religious significance to you; so I’ll leave you to it.
To blame demons for ills is like throwing
up your hands and abandoning any effort to
find out what is really happening and dealing
with it.
Leaping to metaphysical explanations means
not giving it another thought. When Jesus
questions all the avoidance, tell him,
“My dog ate my homework!”
“The Bible repeatedly and emphatically claims there are indeed demons.”
I grew up with missionaries living in our house when they were back in the states during furloughs. The stories they’d tell about demonic activity — and actual demons — were terrifying. We kids weren’t supposed to hear it, but upstairs, supposedly in bed, we’d lie on the floor with our ears pressed to the registers and were able to hear everything. Then we couldn’t sleep. :(
No, it doesn't...
For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God, not by works, so that no one can boast.
--Ephesians 2:8-9--
If you were required to read the entire Bible for salvation, your salvation would have dependence upon something you would do or not do. Such is not the case.