I see Wedge's helmet in the cockpit and two stripes on each of the wings, so we can say with some confidence that it's Red 2. However, the astromech droid is blue and the stripe on the nose is broken so you can't be too sure. (The Red 2 X-wing has the unbroken red stripe on the nose seen on the "stock" X-wings in the hangar, whereas on some other X-wings, such as Luke's Red 5, the stripe is broken. In addition, the astromech droid seen on the Red 2 X-wing at the Battle of Yavin had red markings.)
On top of that the Red 2 X-wing's engines are larger in proportion to the rest of the ship compared to the Red 5 whereas the engines on this one are actually smaller.
Also note that the Red 2 markings should only be present on the outer surface of the wings. However the yellowing around the squadron markings are there so maybe...
The engines lack the red circles sported on the engines of the Red 2 studio model so we can't be too sure.
The bottom "lip" on the nose is missing or not very prominent, whereas on the Red 2 it's a little more prominent than on the other X-wings. However, the Red 2 X-wing sports red triangles near the proton torpedo launch tubes, and there are red tiles at the corresponding location on this model.
It is true that the droid's head should face backwards, but not the droid itself. Remember that in the Yavin 4 hangar scene when R2 was placed into Luke's fighter (as well as after the Death Star trench run when he was being removed) he was positioned so that the "front" side of his body faced the same direction as the fighter. This was also true at the end of the Battle of Hoth. And as I mentioned above, the droid shouldn't be R2-D2.
It is true that the engines and the laser cannons are more accurate than those on the 4502 X-wing, but the main issue is both are much too small. Judging from this
picture I think the engines and the laser cannons should be considerably larger - in fact, 4x4 cylinders would represent the size of the engines more accurately, and 2x2 round bricks the laser cannons (at the point at which they attach to the wings). The engines are also a bit too short ( I remember that they should extend right up to the droid socket, just behind R2) so using 4x4 cylinders would generally enlarge the engines so that they are to proper scale.
The tip of the nose should be a dark grey. I think all of the parts he used for the exterior exist in dark grey so fixing that shouldn't be too hard.
Am I the only one here who thinks the canopy structure is a bit too big
The SNOT wings and the canopy remind me of roguebantha's X-wing...