Pence was warned in writing by several states things were amiss, but he chose to ignore.
This is absolutely false. Some officials in several states may have done this, but there wasn’t a single case where a government official or a legislative body empowered to act on behalf of a state did any such thing.
The States officially submitted one Slate of Electors to consider. Period. "letters" being mailed by someone telling him they believe something was amiss doesn't change that reality or create any mechanism or powers that don't exist. Someone sent letters? What exactly do you think that changes about how the process has to operate?