WELCOME beautiful!!! I'm sorry for the delay in responding to you.
Unfortunately it is not uncommon for Pet stores to make mistakes. Many just don't have the correct information on many subjects from the sex of a bunny to what it should be eating. And it is true that unspayed females have a high risk of cancer in their reproductive organs, and that really should be told to customers so they can prevent it.
First: Does he go in his litterbox still? I mean is he having any trouble getting into his litterbox? I just want to be sure he is not exhibiting any symptoms that could reveal any illness that would be causing a loss of his litterbox habits.
So, with that said, I believe he is doing this because you remodeled your room. Everything looks and smells different and he is "remarking" his territory. At least he is not urinating, but poop everywhere is no fun either! He will stop doing this once he gets used your room and feels assured that he has left enough "messages" telling everyone this new place is his place too.
SO, in order to stop him from leaving poop messages everywhere, you either live with the mess until it dies down OR you establish it as YOUR territory. Which means, the first few days he comes into your room, you shoo him out. Then allow him in, but watch carefully, and the moment he leaves a poo, you shoo him out. This could take weeks but eventually he should give up and see it as your territory.
Let us know how that goes.