The warning signs on overhead power lines concern possible fatal electrocutions. And sources are somehow still missing.
By the way, it's like vaccination here, you don't have to buy if you don't want to...

Since you seem to be convinced that these "side effects" are true (I don't doubt them in any way, but I don't believe them without credible sources), I would strongly advise you not to use an electric blanket. Why? Quite simply, the placebo effect works the other way round too.
This is serious advice, not criticism or anything. Because I am convinced that everyone is allowed to believe what they want and no one has the right to doubt this belief!