Joseph –
“Chareidi butei dinim absolutely do not convert intermarried spouses.”
As usual, you just state without any sources.
Is Rav Chaim Ozer of Vilna considered a “Chareidi” Posek?
Is Rav Shlomo Kluger considered a “Chareidi” Posek?
The very statement of “absolutely” indicates ignorance. As there is definitely a Makom le’Heter (or even a Chiuyuv) if she is willing to accept Mitzvos.
Perhaps you are confusing it with Reform style conversion wherein there is no Kabalos Ol Mitzvos?
As for your original question – bottom line:
A) work on his Kiruv, and after he embraces Judaism, B) see if she is willing to embrace it and seriously accept as well. C) Present the issue to a prominent Bes Din/Posek (or present it once she is process of considering – You are the “professional” in the Kiruv field).
p.s. leave your spear home.