1) His explanations weren't satisfying enough. = This is the correct form. Good job!

1) correct 2) not correct. Satisfying enough? . Also consider: His explanations were not enough to satisfy. His explanations were insufficiently satisfing.

"His explanations weren't satisfying enough" sounds way more natural to me. I would just leave the "satisfying" out, on the second sentence, like this " His explanations weren't enough". It is better to end the sentence with enough