I am slightly unsure about the cost/weight of debt and have received several different opinions but also after reading more I am beginning to wonder

I am slightly unsure about the cost/weight of debt and have received several different opinions but also after reading more I am beginning to wonder if inflation and the stated uncertainty of the operating costs as stated on the second page. Please looking for reliable and confident responses. As far as the WACC, I have tried calculating different ways and have ranged from 6.7% - 9.67%.... Mainly to uncertainty in debt and overall weight to divide by, what should be excluded or included, etc... Please see attached for details.

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