Is he who is ignorant that Allah is not like anything, such as not knowing that Allah is not a light like the light we see, considered an infidel?

Avoid giving in to whisperings (waswas), and know that an ignorant person is not considered a disbeliever until proof is established against him and the religious ruling is made clear to him.

Shaykh al-Islam Ibn Taymiyyah (may Allah have mercy on him) said: "Therefore, no specific individual is to be declared a disbeliever (kafir), or a transgressor (fasiq), or a sinner (asi) unless the Prophetic proof has been established against him. Allah has forgiven this Ummah for its mistakes, and this applies to mistakes in matters of belief (khabariyya) and practice (amaliyya). The Salaf (pious predecessors) used to dispute over many issues, yet none of them declared another to be a disbeliever, or a transgressor, or a sinner. He gave examples of this."