How to calculate CF for particular investor?

Let's assume a company owns a "how to produce tech" and wants to raise some investments for lunching the production by exchanging 30% of its equity for X $ shareholder loan provided by new shareholder. We ignore the equity value as it's relatively small and represent only % of distribution of earnings to shareholders, 99+% of investments provided by shareholder loan..

I need to calculate 2 groups of perfomance metrics (NPV, IRR etc.) for project overall and the investor providing shareholder loan.

So I've calculated the project FCFF (FCFE, doesnt rly matter, there is no other debt or other liabilities except new shareholder loan) then took 30% of it as this part belongs to new shareholder and then subtracted the value of initial investments in 1st period(shareholder loan), added the interest and loan repayments in particular periods and got some kind of adjusted CF for the investor but I guess I am making some double accounting as investments outflow are already presented in project FCFF.

Isn't it a more accurate way to take 30% of Revenue and then make a 100% of regular adjustments to get to FCFF and then add the interest and loan repayments as the whole expenses financed by new shareholder?

Or any other way to get the metrics for this new shareholder?