Shariah Compliance Stock Are also involved in Interest?

As per Shariah Compliant Stocks methodology they are still involved in Interest or Haram income <5% or <33%. I am From Pakistan and we have KMI 30 and KMI ALL which comes under Shariah Compliant Stock,Some Muftis said specially Sheikh Asim-Al-Hakeem (Saudia) they said stock trading is halal but company must not be involved in interest but in my country there is no company is pure from interest, So i want to ask that what if i buy Shariah Compliance stock and give estimate percentage amount from Capital Gain( shares buy and sell profit only not dividend) to charity is this will pure my profit and finding exact percentage of interest is difficult so how i can estimate it can i just used finance cost percentage to calculate and give it in charity? Or if it’s not possible shall i leave it. JzakAllah I will be very thankful to you if any expert advice me in the light of Islam