I have been implementing a LEAPS strategy with ACWI for the past year using these calculations in a spreadsheet. The research I've done on similar strategies say that I need to account for the implied interest and forgone dividends when buying options on the index, and that the total cost should be compared to a benchmark rate.

Are the calculations I am doing correct? If so, I don't really get why buying a similarly leveraged option now with fewer DTE results in a much higher total cost vs the benchmark.