There are huge arguments among various poskim as to whether certain treatments are allowed or not. R’ Chaim Kanievsky holds that most treatments aren’t allowed, even IVF (he heard it from his father). R’ Elyashiv disagrees, and holds that they’re allowed.
When someone is going through fertility treatments, it is very important to have a Rav who knows every aspect of the treatments, and what each one entails.
My wife and I have twins who Hashem sent us via Bonei Olam. We know what it’s like to go through the whole thing, as it took us years to finally realize our dream.
At one point, we were referred to a well known and respected Rav. We asked a shailah regarding a certain treatment and how it affected us. He gave us a psak, and started explaining it, by going through the procedure. He had the procedure wrong! I pointed it out to him, and he told me he needed to do research on it. Often, a decision is needed within hours when it comes to these things, so it didn’t really work for us. I went back to my Rav and told him what happened. He told us to ask our doctor (a frum Jew) if he has a Rav to recommend.
He recommended R’ Willig, from Riverdale. He knows every aspect of every procedure, and is a known expert on fertility treatments and how they relate to halachah.
As for how far should one go, I think it’s an individual choice. It’s extremely difficult, and can sometimes affect your shalom bayis. Every couple needs to know what they can handle, and choose accordingly.