3. Atlas tells me that the GOP came out ahead in the national Senate vote in 2010, 2014, and 2020. Wikipedia also tells me that Republicans came out ahead in the 2020 Senate vote. (I don't think this is all that meaningful a number, but you seem to have that fact wrong.) In other words, they've come out ahead in exactly half of the last six elections. Arbitrarily writing off two of those because they were "landslides" makes no sense.
Well, the GOP won a clear majority of seats up for election in each of those three years, in fact they won a higher percentage of seats than vote in all of them.
The problem really is with the US electoral system, regardless of which party it benefits (mostly the GOP in modern times, but this could change). Of the three federal electoral systems used, not one is as democratic as it could be, which renders the argument that they counterbalance each other moot: the Electoral College is bizarre and arcane, the Senate is hideously malapportioned, and the House uses FPTP, made worse by gerrymandering.
Their voters are better distributed given they tend to be the majority in more states. Nobody is talking about taking away polls in white majority counties and neighborhoods that look Trumpy.
