Aweeee, God bless your heart for loving your furbaby so much. I think it's very normal to worry about our furbabies like that. For those who say, "it's just a dog" well, I feel bad for them, cause if that's truly how they feel, then they've never really experienced the love of a furkid before
When our boxer boy was 2 years old, I got him neutered and he was a hefty 70 pounds then, I still worried like crazy about him. Heck, Maggy has an appointment to go to the vets on the 4th of February and the doc said "we'll see" how she's doing then as to if she can have her first set of shots then or not. I'm scared outta my wits about it and I told my vet that. But, she has to have them. The best I can tell ya hon is to have faith, trust in a higher power if you believe in him and leave it in God hands, that's all you can do. I know times like these are really hard, it's all a part of being a good Momma. Please keep us updated how your furbaby does with the neuter and I'll keep you both in my thoughts and prayers.