Hi @verlakasalt,
In my opinion, the four images you’ve attached are of very good quality.
The images are sharp, well-exposed, with good contrast and natural, well-saturated colors.
Regards
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When I do finally get around to posting my experience with IR dirt detection, I’ve got some results that make both of these observations a little more interesting.
The short version is that it depends which side of the film the dirt is on! I think the halo is something like a lensing effect (or some other physics phenomenon like that) on the “back dirt”. The “front dirt” shows up much sharper and in focus since it’s closer to the emulsion layers that are the focal plane target.
As it turns out, it’s easier to detect dirt on one side of the film than the other when using a separate IR capture due to the same effect. I’m hoping to do a nice write-up with example images of both kinds and the math I’ve cobbled together to make it (mostly) work with Kodachrome. Sorry for the wait in the meantime!
But yeah–you’re not alone–I’ve seen those halos around dirt before, too, even when the frame was perfectly in focus.
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I guess the issue is that dirt can be on the emulsion side, and on the support side… assume the emulsion side is facing the lens.
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I had the same experience, indeed. Maybe that’s a reason for me to clean the films as well. But I find it tricky when it comes to the magnetic sound track that’s on the film. Even though I’ve digitized it well, I still wouldn’t want to mess it up.
I’ve been brave (or dumb? 
) and cleaned all the sound films with a dry microfibre cloth by manually pulling them through and frequently changing the part of the cloth. A lot of loose dirt came off and I couldn’t detect any additional scratches afterwards. I think it was worth it!