1. In a fair investigation or trial lets say someone allegedly assaulted someone but if the person that was allegedly assaulted says that they were not you have no case. You're innocent til proven guilty and if the Ukraine government is saying they had no idea aid was witholded you can't prove a quid pro quo.
2. Thats proper procedure and them not doing it comes across as rushed.
3. Oh okay if that's the case then I do see the case for impeachment under obstruction of justice.
This vid should give you a better understanding based on a few of your points. Different arguments with different justifications. It's not clear that either side is right or wrong, more that they are both simply using the tools and influence available to them, which isn't purely one sided.
The Canadian National Anthem According To Justin Trudeau