I'm surprised no one has yet responded to your post, so let me try to answer a few of your questions:
(1) As for precanceled postage due stamps, they are very common in the US. The quote below explains it briefly:
Quote:
For postage dues, the local post office would precancel these stamps for when someone owed postage due for a single piece or many business reply envelopes. The postage due stamps could be applied to the piece when the payment was made and no further cancellation needed.
The practice of precanceling postage due stamps was discontinued in the 1930's.
(2) The second stamp is definitely a Kansas City, MO precancel that probably met with some debris or inking problem that resulted in the example shown.
(3) The Honolulu set is a very nice start toward a small precancel collection.
As is typical for most precancels, there is little value to most of the common ones, but the challenge of uncovering certain cities and precancel types is an entertaining hobby in itself.
If you are interested in precancels as a side-hobby to your collection, I would suggest you explore this site for further information:
http://www.precancels.com/Hope you find this information helpful.