I think it looks pretty good, Toshi.You underestimate how difficult that kit is to get right.
You could correct the nose wheel without too much trouble.
A good hint for weathering is to work from a photograph of an actual aircraft. The black P-61s were fairly late in the war, and the most significant effect on most of them was just a lot of hours in the air. Missions typically could be eight hours.
You will like the P-40 kit much better. As far as camouflage, just be aware that the seemingly random pattern is actually a pattern. Look at as many photos as you can find to get the hang of it.
When you do paint it, go light first, then dark over. A trick I like- blow up the drawing in the instruction to scale. Lay down blue tape on your cutting surface and tape the plan down over it. Cut out the area you want a mask for (the brown) and put it on the airplane. don't burnish down the edges- leave them slightly up. Then paint; lots of light coats.
Of course you should practice first on some srap.
Good luck, you have the right attitude.
EDIT: one other trick. Figure out where the major decals go, in particular anything with white or yellow. After you've primed her, which in this case might just be a few coats over all of the neutral gray; cut decal sized shapes out of blue tape and put those on where the decals go. The thing is to make them just a little bit smaller than the decal, you don't have to be precise. Leave those masks on through the whole process of brown and green. When you do the decals peel them off, then do the gloss coat, then decal. It helps a lot to make them nice and snappy colored.