Exposure is changing when I export. Even looks different in the preview or screeshot of same screen.

My first thought was also a conversion from 16 or 32-bit. 

When you change from 32 bit linear to an 8 or 16 bit gamma corrected colour space then you need to tone map i.e decide how values in the linear space will be shown in the gamma corrected space. To retain the values shown in the preview, convert to 16/8 bit and choose Exposure and Gamma as the method and leave the defaults (Exposure 0 Gamma 1.0).

Dave

But this isnt the only layer affected. There is another layer that is overexposed when exported or screenshoted which is the dirt that does not have an adjustment layer on top of it but it is set to divide in the blending mode or whatever that is called. I included a screenshot incase I didnt describe that correctly. 

Here are the exposure layer settings I have on the watermelon wagon layer. I was playing with it to get it to look just right like the above on the left, but I also dont know what gamma correction and offset mean.