If a person repents to Allah for abandoning prayer and reading the Quran, while fearing failure and lack of success due to his mother's and sister's prayers against him to that effect, will Allah forgive him and grant him success and prosperity, and will their prayers against him be answered?

Repentance from abandoning prayer is obligatory and immediate. It is a cause for success and forgiveness of sins. Whoever repents with sincere repentance, Allah will forgive him. "The one who repents from sin is like one who has no sin." As for cursing oneself or one's children in anger, such supplications are not answered, out of Allah's mercy and kindness towards His servants. The mother should be advised to avoid cursing her children.