Both sentences are perfect. The second sentence is not past tense. It looks like past tense but it is actually "subjunctive" mood. The subjunctive mood looks like the past tense for all verbs except "to be". For the verb "to be", you say "were" instead of "was" in subjunctive mood. Here's an example: "If I were to meet an alien, I would be happy."

Hi, this is great grammatically but the first sentence sounds strange to me. Without other context, one assumes that him is the same person in both clauses. If you meet him (the meaning of see in this context) then you don't need to let him know, this feels absurd. I would say: "If I see him, I'll let YOU know"

I am so sorry, that was a mistake! I wanted to say that your sentences and reasoning behind it is absolutely correct.