Is considering what the questioner uttered on both occasions to be counted as a divorce – whether it was a self-thought or an audible utterance – considered a divorce, especially since he does not recall the exact wording he used with his wife, nor whether it was explicit or not?

Divorce does not occur through expressions of promise, or narration, or questioning, nor through inner thoughts without verbalization, nor with doubt about its occurrence. What you mentioned are mere whispers (waswas), so do not pay attention to them. What will help you get rid of them is seeking Allah’s help, sincerely turning to Him, and supplicating frequently.