It’s the sentence “A は B だ” meaning “A is B“. The A is お前 meaning “you” and the B is 光 meaning “light” so お前は光だ means “you are light”.
ときどき means “sometimes”.
まぶしすぎてまっすぐ見られない, it’s the sentence “Adjective すぎて Verb Negative Potential Form” meaning ”so adjective that one cannot do something“ or “too adjective to do something”. When the adjective is an i-adjective, so in this case まぶしい meaning “bright”, remove the い in the end and attach すぎて. And the verb negative potential form is 見られない. It is the negative form of 見られる which is the potential form of 見る meaning “to look“ and まっすぐ means “straight” so まぶしすぎてまっすぐ見られない means “too bright to look straight at”.
けど means “but” in a casual way.
それでも means “even so” or “even still”.
お前 followed by the possessive particle の means “your” and そば is “the area around the object” so お前のそば means “your side” or ”near you”.
に is the location particle used with a stative verb. And the stative verb here is いて which is the te-form of いる meaning “to be” or “to stay“.
A verb Te-Form followed by いい means “it is ok to do something” or “can do something”. So お前のそばにいていい means “it is ok to be near you” or “can stay by your side”.
かな used in a question indicates that the speaker is asking a question in a humble way.