Hi atom, welcome.

If you do not know much about stamp collecting it can all seem over whelming at first but don't worry, you don't have to know everything. No one does, really.
Juts take it slow and do what you want to when you want to. Mostly stamp collecting can be relaxing.
OK, for US stamps it would be good to look in a Scott's Specialized US stamps catalogue at the library. Or . . . get the old stamps together, arrange them so that they can be seen and do some close-up pics or better yet, scans, of the stamps and post them on here again, perhaps in a separate topic.
I don't know enough about US material to say what is a possible stamp to investigate further or what isn't.
The embossed stamps printed in / on the corner of envelopes are known as 'cut squares' or embossed stamps and are in the back of the caatalogue, probably listed by the whole envelope. It is still neat to collect the ones cut or torn off and the cancels also. All in all they are probably not worth much compared to the stamps. Not everyone collects them. Generally speaking of course.
Stamps are graded in price and value by their condition and eye appeal. Condition can be a nice cancel also, for those (like me) who collect them and appreciate them all to pieces.

Condition can also be how well the design is centered overall in the stamp. Any rips, tears, thins in paper, scrapes, pulled perfs (perforations around the edges), bends, creases, holes, heavy cancels instead of nice light, clearly readable cancels.
Gum (glue) on new stamps that is undisturbed is worth more than gum that is disturbed or has hinge(s) or paper attached.
To sell on Stamp Community (or email others) you need 50 posts at this time. Selling on
ebay or Bidstart is probably the best shot, if you are knowledgeable about that.
As a cancel (cancellation or postmark) appreciator I can tell you that you have some nice ones. They look nice. Some are known as fancy (cork-carved) cancels, most are the Circular Date Stamp Cancels (CDS or CDC). Some are the duplex (two-part) cancels with a CDS part and a wavey-lined killer or obliterator part.
Mint (mew, post office fresh) stamps or even used, cancelled stamps are generally worth more when they are in corner blocks of four or six or some multiple. Mumbers on the block selvage (margins) mean that is a plate block with the printing plate number on the corner. Worth a bit more usually.
Modern stamps are usually not worth very much.
The prices in catalogues are the prices you would pay a dealer for one really nice copy of that stamp. The price reflects the time it takes the dealer to assess, catalogue, stock and show the stamp to you. His time. Mostly they sell for much less than that. Really nice, really rare stamps (few in number) go for more than the catalogue price sometimes at auction. So a catalogue will give you a general price to compare to other stamps but not a realistic selling street price.
But, I have sold stamps, one at a time, for 99c each or more, on
ebay, because they were wanted because the cancel was nice or the stamp was well centered (not all are) are presented well, or just was selling to the right person at the right time.
If you are selling on
ebay, search on here for tips or start a thread and ask for suggestions.
I can have a go at any Canada stamps you have also, to judge their value. Start a new thread under Canada stamps though please.
Any questions?