It's been a long while since I"ve had to recall the hormonal reproductive cycle. I'm honestly somewhat distracted at the moment, but I would hold off giving oxytocin as long as the tortoise is nesting and not unproductively pushing.

I don't think there is any evidence to suggest that nesting behaviors are directly related to blood horomone levels.

I hope this helps for now, I'll try to get back to you with some more detail.

Ian