Your heuristics are, in my opinion, too conservative or not strong enough.

Track record of saying reasonable things once again seems to put the burden of decision on your subjective feelings and so rule out paying attention to people you disagree with. If you're a creationist, you can rule out paying attention to Richard Dawkins, because if he's wrong about God existing, about the age of the Earth, and about homosexuality being okay, how can you ever expect him to be right about evolution? If you're anti-transhumanism, you can rule out cryonicists because they tend to say lots of other unreasonable things like that computers will be smarter than humans, or that there can be "intelligence explosions", or that you can upload a human brain.

Status within mainstream academia is a really good heuristic, and this is part of what I mean when I say I use education as a heuristic. Certainly to a first approximation, before investigating a field, you should just automatically believe everything the mainstream academics believe. But then we expect mainstream academia to be wrong in a lot of cases - you bring up the case of mainstream academic philosophy, and although I'm less certain than you are there, I admit I am very skeptical of them. So when we say we need heuristics to find ideas to pay attention to, I'm assuming we've already started by assuming mainstream academia is always right, and we're looking for which challenges to them we should pay attention to. I agree that "challenges the academics themselves take seriously" is a good first step, but I'm not sure that would suffice to discover the critique of mainstream philosophy. And it's very little help at all in fields like politics.

The crackpot warning signs are good (although it's interesting how often basically correct people end up displaying some of them because they get angry at having their ideas rejected and so start acting out, and it also seems like people have a bad habit of being very sensitive to crackpot warning signs the opposing side displays and very obtuse to those their own side displays). But once again, these signs are woefully inadequate. Plantinga doesn't look a bit like a crackpot.

You point out that "Even though appearances can be misleading, they're usually not." I would agree, but suggest you extend this to IQ and rationality. We are so fascinated by the man-bites-dog cases of very intelligent people believing stupid things that it's hard to remember that stupid things are still much, much likelier to be believed by stupid people.

(possible exceptions in politics, but politics is a weird combination of factual and emotive claims, and even the wrong things smart people believe in politics are in my category of "deserve further investigation and charitable treatment".)

You are right that I rarely have the results of an IQ test (or Stanovich's rationality test) in front of me. So when I say I judge people by IQ, I think I mean something like what you mean when you say "a track record of making reasonable statements", except basing "reasonable statements" upon "statements that follow proper logical form and make good arguments" rather than ones I agree with.

So I think it is likely that we both use a basket of heuristics that include education, academic status, estimation of intelligence, estimation of rationality, past track record, crackpot warning signs, and probably some others.

I'm not sure whether we place different emphases on those, or whether we're using about the same basket but still managing to come to different conclusions due to one or both of us being biased.