Is separation the outcome of the Istikhara prayer, or do his attempts at reconciliation mean the continuation of the relationship?

The benefit of Istikhara depends on the servant's sincerity, their submission of the matter to Allah, and their reliance on Him. The preponderant opinion is that after performing Istikhara, the person seeking guidance proceeds with the matter unless Allah turns them away from it.

Based on this, since you proceeded with dissolving the engagement after consultation and Istikhara, do not go back merely because he is trying. This is unless it becomes clear to you that returning would be better for you.

We also alert you that a suitor is a stranger to his fiancée until the marriage contract is concluded, and his communication with her should only be when necessary and to the extent of that necessity.