1. It's a near impossibility that this could be the (ungrilled) reissue. In the expanded view, the decorative elements around the design border are weak and sometimes broken so this cannot be a reissue. Otherwise, it's a common postmark of origin with a blot cancel (a minus). The stamp is stained, a big minus and is not well-centered. The railroad corner card/return address is a plus but the cover is cut down and affects the corner card, so a minus there. The result is a cover at the low end of the pricing spectrum. See eBay
"sold" listings for an average price for covers with Scott #114.
2. With nothing remarkable about the cover otherwise, its price is based on the stamp and its centering plus overall condition. The stamp is in average condition. The plate blur is interesting and would add something. But the spotting and staining on the back are a minus. Again, this would be on the lower end of pricing for run-of-the-mill Scott #73 on cover.
3. 1926 Los Angeles-Salt Lake City flight. International or domestic use makes no difference to the value of the 8c airmail stamp on cover except for perhaps adding its value to the overall cover value. I don't know where the pencil pricing comes from, but it's way off. You can find a number of these flight covers for sale online for $5 or less. So one can just add the value of the used 8c stamp and see if anyone is interested in that usage.
4. This is a cover flown from the US by seaplane to be dropped on the SS Leviathan
. It never found the ship and returned, with that cachet applied and the cover sent through regular means to its destination. Another ridiculous pencilled price. Again, check out eBay
SOLD prices for this cover. This is a foreign destination so is somewhat better than a US destination cover.