What is the ruling on fluid that is discharged and has characteristics of both manī and madhī? And does it necessitate ghusl if its discharge is without desire due to excessive washing of the area?

Turn away from obsessive thoughts and do not pay attention to them. You are not required to perform ghusl unless you are absolutely certain that semen, which necessitates ghusl, has exited. If you are in doubt about whether the discharge is semen or something else, you have the choice to assign it the ruling you prefer. The exit of semen without lust does not necessitate ghusl according to most scholars. A person afflicted with obsessive thoughts may adopt the easiest opinions until Allah Almighty grants them healing.