Democrats by principal shouldn’t be supporting Israel’s genocide, but clearly they are. What makes you think third party politicians will be any different? Bernie is a Democrat and isn’t corrupt or pro-genocide. At best I’d say the jury is still out on Jill Stein’s loyalties. Third party politicians can be corrupted, and corrupt politicians can infiltrate third parties on false pretence. No, third parties aren’t the solution to this particular problem.
I have no doubt that Trump is capable of giving the order. As it stands, there is no way the order is obeyed. Trump will of course start trying to install loyalists in military leadership, but I doubt even the generals could successfully get such an order obeyed today. The entire military culture would need to be replaced, and I think the protections against that will require more time than Trump has to do it.
Thankfully, incompetence is a core trait of fascism, and I don’t think Trump or his people have the juice.