hello Christopher - welcome to the GMB. Starting with your final question, regret to say it's policy here that we don't provide values - it's too personal an issue as to what a piece of glass might be worth, and problems could arise if the sale figure didn't match a value we'd provided. Glass has a diverse value to all people, and our suggestion is to look at on-line auction sites where you may find prices realized for very similar or identical pieces.
I'm not quite sure what to make of what appears to be the signature of a very important in-house designer by the name of Kny. Ludwig Kny was the chief designer for Stuart from c. 1918 and was responsible for many of the well known cut glass patterns between WW I and II. Do you consider this to be a genuine signature that's been inscribed into the glass with a stylus or similar, or is it an acid badged effect?
Unfortunately, your pix are a tad small, and I can't see the design clearly enough to match with similar in the books - suggest you post one or two more pix with a first dimension size of c. 700 if possible please.
Specific dating of your glasses is probably a non-starter - as mentioned some of the popular designs were made over many decades, though we may possible be able to help as to when the design first saw the light of day.
Sorry this is rather vague for your first outing - look forward to seeing some more pix.

P.S. In the meantime you might try looking at the Replacementsdotcom site at their Crystal section - most of the C20 glass houses are represented, and you should see a surprisingly large selection of designs under the Stuart name.