I've seen polls showing that his numbers went down. On net, that seems to be what happened so far. You looking at Gallup for indepedents? It's all speculative, but not pressing for impeachment proceedings comes across to me as a more problematic path.
Impeachment might be an option but remember that much of the electorate is misinformed and of low interest in details.
Look at it this way. The Attorney General has determined that not only was Trump innocent but a victim and I expect the people I am thinking of might see Trump as a tragic figure.
So jumping on impeachment which was supposedly based on what Mueller came up with was sabotaged by Barr.
Rather than beating that horse on the respirator to death, don't focus on "collusion". Instead go after his financials and expose them. Certainly NY has found sufficient grounds to go after Trump and his family, merely waiting for a chance. Focus on Trump for criminal activities (that worked against the mob and Enron after all), things that are harder to wiggle out of. Right now impeach is a losing proposition of petty revenge at least seen that way by a sufficient number to perhaps not vote for Trump but stay home and the Dems suffer.
So what?
1) Use every legal mechanism to obtain documentation and then go on that. Send Barr recommendations to criminally indict the head of the IRS, Mnchen, then when Barr fails to act in a timely way hall him before Congress and read the law to him. Then onto the courts without the DOJ and perhaps have those who are uncooperative held in contempt of Congress and jail them.
There is one shot at the king, Any impeachment requires a good chance of putting sufficient pressure on Republicans to give sufficient support for removal in the Senate. The consequences of failure could be catastrophic.