Congrats on the new addition! He sounds super adorable! 
The pen is his territory, and since he isn’t neutered yet, he is territorial like all bunnies are. So when you step in, you are intruding on his space and when a bunny sprays that is them marking their territory. So when he is spraying you, its him being territorial.
Territorial issues should go down after neutering, and after their hormones die down. Which should be about a month after neutering. Thats when i personally would try bonding with him again.
After his surgery just let him chill out for a while, you want them to be calm and warm after surgery. From what i have read, rabbits are more prone to hypothermia after surgery because of the Anesthesia and their smaller size. So make sure he is warm for the first few days.
Neutering also helps a lot with litter training, so after his surgery and his hormones are calmed down, he will be much easier to train!