Then there's the uncertainty of finding the realm heart, even if the egg hatches and becomes a child of the realm. He knows about this uncertainty, but he can't fix it. This is the best that he can do.
This was a plan he and his father made before the turmoil of the godling that appeared in the dragon's home plane. It wasn't supposed to be like this. He was supposed to have the help of the dragon spirit in this plan, and it was highly likely that the plan would succeed since something like this had been done before and the dragon spirit had been able to directly find the realm heart through a child of the plane before.
At that time, the dragon spirit had used a dragon that was a child of the plane to access the realm heart and try to take over the position of the realm lord and Will of the plane at the same time.