I had a (micro)prolactinoma that was successfully treated with medication. Even though it was nowhere near as "bad" as this man's girlfriend's, getting it diagnosed took almost 2 years and the possibility of prolactinoma was dismissed outright by several doctors.
It should be pointed out that the pituitary gland sits at the base of the brain and prolactinomas are not technically considered "brain tumors" because they're not in the tissue of the brain. So it's a mischaracterization to keep referring to this as a "brain tumor" and a bit of an odd one for someone trying to start a medical research effort.
Unfortunately, the reality is that sometimes life just doesn't deal you a good hand. I think it's sad this man is talking about children when prolactinomas are a leading cause of infertility and it sounds like, for a variety of reasons, this man's girlfriend has one that is very difficult to treat. While it's OK to always hope, it's also possible to cling to false hope so strongly that it prevents you from accepting and moving forward with the life you have instead of the life you envisioned.