I see you've gotten to a point where most of the mass-tagging is done and now a more detailed approach is needed,
so now you're finding the limitations of this humble script.
There are some tricks that may help you. I hope.
a) If I call your script for an entire album and the result will show tracks from two (ore more) different albums, how can I select just one of this received albums and apply only the changes from this one selected album?
So, you select only tracks that are supposed to be from the same album, but in the results some show up under, lets say, compilation albums, others in singles and others in studio albums.
How to tag them all under the same album?
Well, if you want to keep the correct ones and quickly disable the ones under the wrong album just right-click each track in the results. A track in the results has a grey background, right-clicking it anywhere is going to disable its check-box on the bottom panel.
Or, if your current tags are very bad, like "Track 01", then first use the "Acoustid Fingerprint" mode or "iTunesMonkey" mode, disabling the album tag or just ignoring it for now so further searches may get better matches.
Maybe edit the properties of those tracks yourself and change the album for all of them with the one you want in the results so the script will prefer the matches that have a similar album name.
And last, or at any point, try using the "iTunes Album" mode. Use the drop-down on the top of the window to see if you're preferred album is in there. If not, use that drop-down to write the name of the artist and the name of the album, like "the doors strange days", press enter and you'll get multiple albums listed in the drop-down. The script is supposed to auto select the one which best fits all the tracks you selected.
b) Which values do I have to adjust in the score configuration to achieve the following:
I prefer results from the original album before a 'Best of' or 'Ultimate' collection type album.
How can I control this?
I'm sorry to say there is not real way to control this.
If the metadata came from MusicBrainz, for example, it would come with information about the type of album, single, compilation, etc., but the iTunes API doesn't provide that.
Aside from already having correct or close to correct album tags so the script prefers a similarly named album the other way to influence results is using the "iTunes Album" mode, as explained in the previous answer.
c) I try to get the result for a sampler like "100 Top Classical Songs". Your result brings back dozens of different albums. I realize, this must be a 'wild' compilation. But hey, why not take the much better titles? But only the titles please.
How can I do that without DEselect every other information on all the dozens of albums?
So, for some tracks, you only want to get titles and maybe artist names.
You can quickly access the iTunesMonkey options by clicking "options", which is on the bottom left side of the results panel.
In the options, under "Replace", select only the fields you want.
I hope those answers are helpful enough.