You literally said exactly that:
The Nixon impeachment was based upon the criminal Watergate incident, so yes, it was a criminal proceeding.
Only in your own mind buttercup. Keep stretching for any warped semantic interpretation you can manage.
No that's literally what you said. He quoted you directly.
Impeachment is only for removal from office. Impeachment can not extend further than removal from office. A president, or any citizen, can only be charged with a crime in a criminal court - the kind with lawyers and judges. Congress is not a criminal court. (although the Chief Justice is required to preside over a presidential Senate trial)
The house can impeach the president for something that isn't a crime.
The house can subpoena the executive branch even if they don't think a crime has been committed.
Impeachable does not equal criminal.
Criminal does not equal impeachable.
The president has no right or legal standing to declare his own impeachment invalid. It's pretty ridiculous this even needs to be said.