you can use turbidometric method of assay where you can measure turbidity at 530nm and compare it with a standard.

Do you mean the microtiter  plate method? Try disc difussion method

very simple method by TLC , spray the TLC with microorganism and incubate it , then spay wth the plant extract leave it and see the results

i think in this case either u purify ur sample and try on HPLC , or buying standardsvfor ur work

For anti-fungal effect you can use that