Is it valid not to perform ghusl after verifying the presence of a white, watery discharge with a faint odor upon waking and suspecting the emission of semen due to waswas, given a good knowledge of the signs of semen emission?

Leave aside these obsessive thoughts and pay them no mind. Whatever the devil may portray to you, that semen has exited from you, do not pay attention to it. Continue with your acts of worship normally, and do not rule that semen has exited unless you are absolutely certain, a certainty upon which you could swear an oath. The white fluid you mentioned is most likely ordinary vaginal discharge. If you doubt whether what has exited is semen or something else, then choose and let it be ruled as you wish.