Hi Ben,
I don't presume to know the answers to your good questions, but in the past 4 years of my search to learn all I could about Afib/ablations I never came across anything that would lead me to believe that your ablation is not successful because your heart rate didn't go up.
The lower heart rate is certainly more comfortable. My rate climbed to 110 today, and it hasn't been lower than 102 since I came home. Dr. Pinski called me today for a progress report, and started me on Atenolol 25mg daily. Within one hour, my heart rate is a comfortable 86 and my systolic B/P came down 20 points. He said I am having an acute inflammatory response to the ablation.
As long as your rate is sinus in origin, that's all that counts!
Be well,
Marian