In addition to what Elwood has so eloquently stated, here is my 2 cents.
1) You did not "invest" any funds in the company by way of the 15% wage reduction. You took a pay cut, period. How many more times does this have to be explained?
2) Your adjusted gross income is based on the amount shown on your W-2 which is exactly what you were paid, i.e. the lowered pay rate, not some imaginary number.
3) Whether you invest in stocks or any other asset, you actually have to have a cost basis for that asset and then sell the asset in order to have a capital gain or loss.
4) You are not diverting any money from your wages into a 401-K which is why there is no deduction from wages shown on your W-2 for a 401-K contribution.
I think your accountant needs to go back to school for a refresher course.