Do the doubts I had about the creed, which disappeared after research and study, count as real doubt that expels one from the faith and necessitates renewing the marriage contract?

The whispers of doubt that a person dislikes and struggles to get rid of do not affect the marital bond, for they are not real doubt. Doubt is hesitation that negates certainty. Whoever embraced Islam with certainty does not exit it except with certainty, and remains in their Islam unless a clear determinant removes them from it. It is preferable to act in a way that keeps a Muslim in their Islam, even if there are many interpretations that might suggest their disbelief.