@Gravellilac, Great news wrt Gravel acting more normal - and eating - after the anesthesia wore off. As JBun mentioned, anesthesia can take a day or longer to work out of his system.
We've had some super concerning situations with post-op recovery of our rescues and adopteds. I won't list them all in this reply. With our last agouti neutered in May of 2022, his neutralized sacs had a "ton" of bruising. I won't post the archived images 'cuz they'd need a trigger warning. I was in contact with our trusted DVM who did his neuter. The bulging did not dissipate until a week or so later. I took photos every day for my log and to show the vet.
He did receive his usual 3 days post-op meloxicam for discomfort. Plus we extended the dosing timeframe.
From our 20 years of taking buns to be sp/eutered, we've only had a few exceptions of post-op recovery concerns. I hear you on being concerned when someone is not following the normal "bounce-back" to normal behavior routines. JBun posted excellent links.
No worries about overthinking! Did Gravel let you take a peek at his incision and deflated testicles?
I love the honking sounds. Our n/male would honk, hum, and buzz around hubby's feet for more than a decade after his surgery. He lived to age 12.
We have a 12 y.o. spayed female with spondylosis who also gets excited for her joint support tab each morning and will verbalize with humming and circling.
I look forward to more photos when you wish to share.