I just read through this thread and this is what I am gathering is Jeff's argument.
The impeachment inquiry is a sham because the whistleblower did not testify.
The whistleblower is a "crucial material witness" who "actually didn't personally witness anything" and "100% of what was cited [in the whistleblower report] was at-best secondhand info".
Based upon his argument, it seems like Jeff is claiming that any whistleblower complaint that the IG gets he has to throw away if the "firsthand knowledge" box is not checked. And the fact that the IG actually LOOKED at the complaint and potentially event independently corroborated some of its claims (from people WITH firsthand knowledge) SHOWS that the process is irrevocably tainted and needs to be fully investigated be for impeachment can proceed.
Then, Jeff claims that the fact that the whistleblower contacted the Intelligence Committee Chairman's office and asked for advice on how to properly file the complaint is somehow underhanded and ALSO taints the process.
His first point is very effectively countered by his second being BS (you are not a "crucial material witness" if you only have "at-best secondhand info" so there is no need for you to testify).
The third point is also easily knocked down. The IG is not supposed to forward a complaint on without firsthand knowledge confirming it but, there is no requirement that the first-hand knowledge COME FROM THE WHISTLEBLOWER. There are MANY points that the IG could have verified. The easiest probably being whether or not the call was in the secure system. And, the whistleblower is not involved in THIS process. The whistleblower's "process" ends when the whistleblower report is filed. This is just the IG. If you want the IG to testify, feel free to call them. But this is no basis for the whistleblower to testify.
As for your fourth point, I see nowhere that says it is improper or violates the process for the whistleblower to contact a congressional committee. The only point where it affects the process is where, on the "Disclosure of Urgent Concern" form they are supposed to disclose if they have "filed your complaint with any other entity, including other Inspector General offices, and/or Members of Congress". But, I have seen no indication that in the course of their contact with Schiff's office they "filed [their] complaint", so I do not see how "process" was violated by them not disclosing their contact.
But regardless, Jeff makes a good point. Impeachement is a rare process. Which MEANS that there is VERY LITTLE ESTABLISHED PRECEDENT to follow. You claim that the "process" is being subverted, but there really IS no "process" to subvert. BECAUSE this is so rare, they have to sort of make it up as they go.
AND this is also not a legal proceeding. It is a political proceeding that, because of lack of precedent, pretty much is only constrained by what is written about it in the constitution. There is no real precedent on what is "admissible" or not, or that any "taint" (by your subjective definition) in the process would require that Trump get off on a technicality.
Basically, you are making up excuses for Trump as you go (and actually fabricating supposed violations of process that are not evident) and trying to discredit the whole proceeding by pretending that your excuses have any sort of constitutional foundation or foundation in precedent.