Absolute approach with multiples

i usually tend to value companies on a catalyst/upside/downside scenario based approach and try to give a sense of the possible variation in % as i believe that, while time consuming, it is a pseudo solid way of not getting totally toasted by the investment experience.

that being said,i've always tried to link the multiples to fundamental things and consequently researched as much as possible, on this forum, on the internet and on different books but still fail to look for a comprehensive and flexible approach. for instance i found a multiple primer on the internet (NYU) which was helpful but rather limited in the way that it offered formulas with consistent limitations (=no flexibility) in the way they approached factors which affect the price of a stock.

first of all, i'd like to find some formulas that link
-growth (of cash/earnings/rev) to capital necessary to support said growth (i know that if you do thing by the book you should be able to deduce it from the overall industry/microeconomic/financial analysis but still)
-something that links PE to the required return on the stock expected by investors rather than the cost of capital (and planning to use it in a "reverse engineering" fashion)

am i overthinking this or simply going wildly off road speaking non sense?