With 4,000 miles the chain and sprockets should not be worn out even with less than ideal maintenance. The marks on the swingarm are not always accurate. They are off considerably on mine. When you roll the bike with it in neutral and the engine off the noise the chain makes should be smooth. The teeth of the rear sprocket should be in the middle of the chain with no binding on the side of the chain.
I doubt the the front sprocket is on backwards. It is easy to check. Take off the cover and look at the sprocket. If you can read the writing it is on correctly. While you have it off clean out all the crud that accumulates in there.
I doubt the the front sprocket is on backwards. It is easy to check. Take off the cover and look at the sprocket. If you can read the writing it is on correctly. While you have it off clean out all the crud that accumulates in there.