The line between law and politics is drawn in the sand, and changes as the winds shift. Like porn, we know recognize it when we watch it, even though we can't define it. A labor-intensive solution (is there a problem?) is to collect all of the impeachment questions and answers and write a community Q&A whereby 80% of impeachment questions will have been answered.
I disagree with the premise that impeachment is an intrinsically "political process", and the Constitution supports me because the process is by law very different from the process of passing a law. It does not strike me that we have been inundated with masses of OT political questions; if in fact we have been, someone might collect up examples, so that we could study them and see what needs to be changed, if anything.
I should also point out that "off-topic" is technically a clearly-defined class of defects, and "being political" is not part of that clearly-defined set (it's in the porn penumbra). We have substantial disagreements over the scope of politics qua OT topic, for example, many people reject questions that ask "why is X the law". I don't, because there are very often legal answers. Still, there is a trend in legal theory that abjures "why" questions, which is about as strong as the trend that demands "why" questions (natural law vs. legal positivism being old-style examples). Questions that call for opinions are clearly off topic. What are the examples of impeachment questions what are not opinion questions?
It is not an accurate statement that "rules that govern Impeachment are determined by the House of Representatives, and the Senate on a case by case basis". Instead, the Senate and the House have rules, and they have the power to change those rules. The constitution does limit the Senate w.r.t. impeachment – they can't go for a simple majority for conviction. Most of the questions that you propose are answered or not very good (not sure they are actually OT). First off, the impeachment part is done, and yet the media still refers to the entire future process as "impeachment", so fine, "impeachment" has a broader meaning in popular use that what etymology and the Constitution would tell us. What happens after someone is impeached? Well, I dunno, they have to live with the shame. They get fired, that's obvious. That question should be closed as "too broad" (or whatever the current version is called).
I don't see that there is a problem that needs fixing. We survived the GDPR freak-out, I think we will survive the impeachment freak-out.
It also occurs to me that people may tend to see impeachment as being "purely political" since (per the US constitution) it is "not justiciable", as only recently definitively determined with the cases of the judges Hastings and Nixon. Again, if you define "capable of being reviewed by courts", then impeachment is mostly not justiciable, except of course if the Senate opts to require a unanimous vote or a simple majority for conviction. But I don't agree with the premise that "the law" is exclusively about "matters that a court can rule on".