I’m worried he’ll hate me, scared he’s going to recover poorly, nervous his personality is going to change, all the irrational thoughts basically. Would love some advice etc!
I can tell you from personal experience with double-spays, single-spays, dental work, etc. that it is 1000% normal to drive yourself insane on surgery/anesthesia day. Your mind perpetually races through the worst-case scenarios and everything in your universe feels off-kilter until you put your eyeballs on your post-surgery bunny.
Accept that you're going to drive yourself insane and do what you can to tame those emotions . Do what you can to take your mind off things for as long as possible. Nothing that you do or think or experience between drop off and pick up will - in any way - alter the outcome... and you already knew that. Take a deep breath and then get through the day one step at a time.