It's strange, I haven't seen Windows Defender trip on it on any of the other computers I tried it on. Is your Windows Defender up to date? The "ml" at the end stands for "machine learning" (meaning AI detection) which is a nest of false positives, but they usually fix it pretty quickly. Anyway, the game doesn't do anything my other games don't. I hope you will be able to enjoy it soon! ;)
There is indeed a bug, thanks for reporting it. It's not exclusive to the Vengeful Talisman: if you equip a talisman, save and reload, you can't unequip it afterward.
Problem is: I can't submit bugfixes during the jam's voting period. But in the meantime, if it really hinders your progression, I can upload the patched version on Google Drive.