The problem isn't so much that there's too much weathering... it's just that it's not really realistic. There's a relatively indiscriminate layer over the entire aircraft, and though that's fine for a 'base', you really do need some area-specific weathering. On top of that, your area weathering doesn't really resemble much what you'd see on even the most heavily weathered aircraft.
To be honest, I feel that many aircraft, particularly German, in game are extremely over-weathered. Really, although aircraft did start to look weathered as time went on, in very few cases did the aircraft look like total chit. There are probably several reasons for this, I imagine some of which is related to moral. The Germans really did take pretty good care of their aircraft, early in the war they even painted over areas along the wing roots in black to hide the exhaust stains. This practice became more scarce as the war went on, but general cleanliness of the aircraft remained.
Generally, as time went on, aircraft did become visibly weathered, but it was not in the way you have it. One of the big things is that the paint, which from the factory was fairly bright and sharp, with a fair amount of contrast between the colors, would wear down and become darker and less sharp and contrasting. In extreme cases, and in areas of high traffic (pretty much just around the wing root, where pilots had to walk over to get in and out of their aircraft), the paint would completely chip away revealing the dulled metal underneath. This is very common on all Luftwaffe single engined fighters around that area.
In your specific case, the fighter you have is most likely over painted in temporary, or maybe permanent black. In either case, especially considering it was in use for a year, this would start to wear away in some areas and reveal the 74/75/76 finish underneath. These types of finishes also tended to either overlap or not quite meet the markings that were not meant to be overpainted (which was almost always only the fuel filler triangles and the crosses).
Another thing largely absent from your 109 is really localized dirt. This would particularly be around the radiators and landing gear fairings.
The big thing, in my opinion, is to remove yourself completely from the presidents of other skinners, not using their work for reference, and really completely on period photographs. This will give you the most accurate, and thusly in my opinion the best result.
