It's good that your vet is taking good precautions. A plus though is that there are now safer anesthesias available and vets are spaying and neutering as early as 8 wks as long as they weigh in at least 2lbs. Also, as long as his "pom poms"
have dropped and everything is normal the surgery will last TOPS 10 min.. 15 is pushing it.. And if you're still really worried maybe you could consider leaving him overnight so they can monitor him for a more extended period of time to make sure he is adjusting well. I hope everything goes okie day!
It's ok to be nervous, it's bc you love him so much!