Knowing that someone is misguiding people from islam, yet not doing anything

Assalam o alaykum I have a problem A few years ago I had a fake instagram account where I used to chat with people etc. so there was this islamic post where I commented and in the comment section I communicated with an ex muslim guy (I know this was sinful as I am a female). I cant remember the matter we were discussing, but I remember we discussed something related to Islam. He said that he used to be a hafiz and that he teached in a mosque in his country. He sent me a video privately og him disrespecting Quran and other islamic books by trowing them on the floor. He also read from the Quran. He told me that his family gave him time to repend. But he said that he will never go back to Islam. He also said that he is working in a mosque and misguiding the children there to not belive in Islam. He also said he will marry a muslim woman and probably just fake being a muslim. He told me his name (which I remember) and the mosques name (which i dont remember). Now I feel guilty that I did not do anything. i could have sent an email to the mosque pr something. I thought that several times but out of either laziness or fear i did not do anything. Am I sinful and responsible for the people he have misguided from Islam? Am I sinful for his marrige with a pious muslim woman? Am I out of the fold of Islam as there may be people misguided from the religion? Im am feeling that I am sinful for not doing anything while I knew about all this. Please help. What makes a person out of Islam? What should I do? Is my sin unforgiveable? What can I do to repent in this situation. This happened a few years ago and I have felt this guilt everytime I think of it. Also whebever I pray (i dont pray usually, but I am really wanting to be regular) I feel that my prayer will not be accepted because maybe because there may be people misguided from islam, by thag guy, Allah will bot accept my deeds. I know Allah is the most forgiving, but all these thought comes to my mind whenever i try to focus on religion. I feel that I am guilty because I knew all this and yet didnt do anything. Plz guide me. Jazakumullah o khairan