(1) Prop looks like a Rotol to me, although the spinner is more pointed than in some photos where the Rotol prop is identified. Unfortunately Mason's book (see below) doesn't detail individual aircraft or production batches very well. The splintering of the prop blades as shown in the photos in your link also suggests the Rotol prop (blades were made from a pressure-bonded wood material, called "Jablo"). I'm willing to be corrected on this point, though!
(2) According to the page you linked (very interesting, BTW - thanks!), "She was still fully armed with the original twelve 0.303 inch Browning machineguns." Francis K. Mason, on page 115 of his book "The Hawker Hurricane" (Aston Publications/Motorbooks, 1987), says, in reference to the start of operations by RAF No.81 and No.134 Squadrons at Vaenga on September 12, 1941, "...none of their aircraft possessed more than six guns apiece, the other six guns having been removed before flying off HMS Argus to reduce weight." He goes on to say that eventually the removed guns were delivered ashore at Archangel'sk and reunited with their aircraft, apparently after Russian armorers fabricated new blast tubes to replace ones that went missing along the way. So, twelve guns it is.
(3) Your guess is probably as good as anyone's, unless further information from the recovery becomes available to clarify this point. What you say sounds sensible to me, but that's only MY opinion!
(4) That sounds correct for the period when the aircraft was built. On both of points (3) and (4), I'd be inclined to believe the artwork on the page you linked. It appears to be based on actual inspection of the aircraft itself.
The addition of the RS82 rockets and their launch rails is a neat feature which will add some great visual interest to the model! These parts can be obtained from several 1/72 VVS kits, such as the Toko/Roden LaGG-3. Nice photo of one of these rockets on the linked page. Go here for more details on these weapons:http://vvs.hobbyvista.com/Markings/bombs/vvsord.php