I've tried to use the Period-Luminosity relation formula which I found on " https://de.wikipedia.org/wiki/Perioden-Leuchtkraft-Beziehung " but it seems to be quite unaccurate. Do you have some other more precise way to calculate the absolute magnitude of a Delta Scuti variable?
You might want to look at the recent paper by Barac et al. (2022 MNRAS and also in astro/ph) titled "Revisiting bright 𝛿 Scuti stars and their period–luminosity relation with TESS and Gaia DR3". The url for the arxiv version is https://arxiv.org/pdf/2207.00343.pdf. Perhaps their P-L relations will help. There is some intrinsic scatter in the relation. Gaia absolute magnitudes might also be directly helpful for some variables.