Where does the last paragraph of what you (adywan) quoted come from?
They say six minutes of Biggs were trashed. I haven't timed the Biggs scenes. I suppose we could assume it was both the Yavin and Tatooine Biggs scenes, but until somebody times them we don't know that for sure. So some of the Biggs stuff could have made it into the final cut, like the short Yavin Biggs scene the Star Wars Unauthorized Compendium claims was in there.
The different creature you mention Han meeting instead of Jabba actually was Jabba, as Marvel envisioned him. But maybe they could have seen a Jabba scene with the human Jabba in the screening, because the comic seemed to be doing its own thing with Jabba. The script (which they were supposedly working from) describes a sluglike Jabba but the comic didn't follow that. Or if they never saw the Jabba scene Lucas could have added the Jabba back after, though I do think that's unlikely. From what Thomas is saying they had the comic already made up and printing when he saw that screening, so what they saw in the screening wouldn't necessarily have affected what ended up in the comic.
Thomas remarks on the Anchorhead group of friends scene being missing because it was in the comic. But the Jabba scene was in the comic too, so why didn't he remark on it being missing if it wasn't shown at his screening?
From that last paragraph it sounds like the Biggs scenes weren't cut until after the preview screenings, except (presumably) for the one with the other friends, which Thomas mentions being gone.
Thanks for the article(s) anyway. Though I'd appreciate if you could say where that last paragraph (the one where they mention cutting six minutes of Biggs) comes from.