Definitly acid damage.The rims are the first to be etched away and are missing. Also the thinning letters.Both are signs of an acid etched coin. Considered damage with no extra value.
No need for a poll. What you have is a dime that has had the reverse filled in with something. You may be able to remove it. Considered damage and adds no value.
It is called "Brockage" and no yours is not a Brockage error. Also please specify where you see DDO. Your pictures are too out of focus to see any detail.
Die cracks are fairly common on the hoof, must be a weak spot. I would say that you have Round Back 9 Straight 4 Wide Date Pointed 5/5 touching ring. As far as I know there is only one variety where the 5 touches the ring so that is a good find.
Discolouration is not an error as it happens after the coin left the mint. Yours has just been environmentally damaged. If you were to rub the high spots, it may start to come off.
That was a "Life In The North" commemorative quarter with a beluga and bowhead whale. Some were issued with a frosting and others were plain. There was a total of 12.5 million produced so they are not hard to find.
Still within specs, especially during the war years when quality was not a priority. Most collectors like at least 90 degree rotation, 180 degrees is ideal.
No its not. A coin wrapping machine usually leaves a thin scratch around the coin. This has material removed which could only occur from some sort of machine that you insert the coin in such as vending, slot, parking meter etc.