1). That doesn't absolve someone of the crime though. And why hold back thousands of documents and prevent the entire executive branch from testifying if you aren't guilty?
2). I'll have to look further into what they should have done.
3). And just for the record, the House did ask the courts about the subpoenas. They said it's not our jurisdiction.
I do think it's very sketchy how the Trump admin was trying to keep things under lock and not complying with Congress and impeachment for obstruction does nakes sense but there's no solid evidence for impeachment for the quid pro quo since Ukraine is saying they didn't know about the withheld aid.