Is a person excused for obsessive thoughts, no matter how great they become? And is suddenly hearing abusive language directed at Allah and the Messenger and imagining a response to it considered an obsessive thought? And is it obligatory to abandon repeated ritual bathing (ghusl) and the declaration of faith (shahada) with the intention of embracing Islam due to the inability to differentiate between obsessive thoughts and deliberate actions?

What you are claiming is merely imagination and waswasa (whispers), stemming from self-talk and the whispers of Satan. You are not held accountable for it religiously as long as you do not act upon it or speak of it, based on the Prophet's (peace and blessings be upon him) saying: "Indeed, Allah has forgiven my Ummah for what they talk to themselves about, as long as they do not act upon it or speak of it." The danger lies in surrendering to it and indulging in it. Its cure is to completely disregard it and fight its satanic thoughts. The occurrence of waswasa accompanied by intense dislike for it and pushing it away from the heart is a clear sign of faith, and it is like fighting an enemy.