I think the difference is that they are corrupt for their own state interests.
It's easier to manage 50 corruptions localized to their individual states, instead of the collusion of corruption at the federal level that is nationalized against the states and the people.
At least with the states, you have the self-interests of the other 49 states to balance the corruption of a runaway state. National corruption ends with weaponizing the arms of government against its people in order to protect the establishment.
RE: #4 - The money... let's think it through.
I think that doing away with the elections will dry up the existing money spigots, such as McConnell's NRSC. What legitimate FEC filings would explain why he raises the money if there are no Senate elections? What reportable expenditures could he make that's not an out-and-out bribe to state legislators if there is no state election, just a vote in the legislative chambers?
He will have to rebuild a new power network to replace it, since it would be harder for McConnell to use national money to influence the state appointment in Mississippi or Alabama, like he's done in the past. There would be no more primaries and run-offs to influence, and no general election to dilute with fake candidates to split votes.
I'd like to hear how you view the role of money in a non-elected Senate.
-PJ
Weren’t Federal Senators chosen by state legislatures prior to Amendment 17? I don’t remember quite that far back. But even if they are appointed, that’s where some money can change hands.