At what age do testicles drop on bucks

I wouldn't worry, buns take a while to settle after the stress and disruption of being away plus having surgery. Neutered buns are normally better with the litter training too, so that might improve.

Lots of healing vibes

Thanks Sparky...he has had absolutely no swelling or redness, really looking great. The next step is trying to introduce him to our Josie and hopefully she will let him cohabitate in my office. We're going to try their first get-together at a hoppy-hour so we'll have the help of more experienced rabbit people, should we need it.
Wish us luck!

How lovely you can go to hoppy hours! If they are accustomed to each other's scent already it may facilitate them seeking each other out.

Good luck for the bonding!

I know how nerve wracking it can be but it will be worth it in the end, and it's great that you have the help and experience of those at Hoppy Hour as well