The seats were canvas. Now what? I am not a happy modeler right now.
It isn't an issue, we all learn stuff as we go. The weathering on the seats you did is really quite good. Learning how to do research to get ideas of how it is supposed to look has a pretty rough curve to it. Been doing research for a long while and been researching VW's since the 80's since I was collecting the real cars back then. You might be amazed at how much people "don't" know about the old VW's and beetles.
As to weathering here are some things to think about. German armor and aircraft early war had good paint and were quite well maintained. The paint didn't chip and flake off like an old piece of machinery left in a field or an old truck up north where they have snow and LOTS of salt. Sometimes a little weathering will give more effect than a lot. If you think you have over weathered the seats a bit, just make a bit of a wash of the brown paint and lightly work it over the areas you want to un-weather or to lessen the weather. The brown color is fine for the most part. Keep in mind that the photos I posted are restored vehicles. While the restorers try to return them to as close as possible to original, in some cases it is best guess or closest material available.
Someplace I have some OLD film photos of a couple of mostly original "unrestored" Kubelwagens that I got to crawl all over. Someplace.
So, don't sweat it. If you now don't like the seats change them. Part of building is also figuring out how to fix OOPS, or make changes.
On my Ju88 build, I ripped out the old Eduard PE control and instrument panels (which would have looked perfectly fine to most folks) and replaced them with newer Quinta Studios panels. Was a bit of a "Oh crap, do I really want to do this?" decision, but ended up being no big deal and they now look SO MUCH BETTER!
I learned years ago that fixing screw ups taught me more than I ever learned from a straight build that went together without a problem.
This plane was my biggest FUBAR:
It is a 1/72 scale He-51 Floatplane put out by Hasegawa. I had it assembled and was putting paint on it. The paint was not going on very well and I decided to strip the paint and redo it. At the time, Easy Off Oven cleaner was basically used to remove paint and chrome. (1980's the dark ages). So I was removing the paint and the whole model started falling apart. the wing struts broke off (fell off actually) the whole thing fell apart into big pieces.


I cleaned the pieces put them in the kit box and set it on a shelf for about 6 months. Finally pulled it out again, (yeah it was a disaster) and redid it to a greater amount of detail than I had originally. It got me several 1st place awards including at a IPMS Regionals. If it had just gone right together to begin with, it would NOT have turned out as nice, and I learned a lot from fixing it. Most folks would have pitched it.
BTW all the rigging is stretched sprue. This model is now about 35 years old and I am as proud of it now as I was back then.
Don't sweat the small stuff my friend.