I don’t yet see the temperament of the electorate to deliver the result that you predict. It’s certainly possible and the trends are going in the right direction. But, the nation is still evenly divided with respect to the President and the disdain for the Congress must fall on the Republicans more so than the Democrats because the GOP controls both Houses. Add the special sauce of the media propaganda and the probability of your outcome is pretty low. The Democrats still want to impeach Trump and they really believe the Blue Wave nonsense. The electorate will remain indifferent to the mid-term election and if they vote, they will more than likely vote based on something that they heard from CNN, CBS, or the Today Show. You already know what the media will say, regardless of what happens in Washington between now and November.
The good news is that the result will probably mirror the 2016 election, so we will see gains in both the Senate and in the House, but the numbers will be single digits in the Senate and low double numbers in the House. Continuing successes will bump those numbers somewhat, a big blowout is not going to happen.
I'm going to take issue with this sentiment. I'll bet dollars to doughnuts, that the vast majority of the disapproval of the congress-critters is the frustration that one's party doesn't accomplish what they want accomplished. In other words, conservatives are frustrated with the republican elites for not pushing through the entire Trump agenda (see also Paul Ryan and Mitch McConnell) more quickly and approve more judges quicker. The liberals are frustrated that the democrats weren't able to stop certain portions of the Trump agenda (Tax cuts passed, regulations reduced, withdraw from the Paris Accord, etc.) and aren't currently impeaching him, or having him indicted through Mueller.
Hence, when polled, neither the republican constituents or democrat constituents are happy. The result: 15.1% approval and 73.6% disapproval (Real Clear Politics average of seven polls). Its equal disdain. Therefore, the mid-terms will come down to turnout.