I have not been investigating this directly as I'm not in your husbands situation but from what I've seen from a number of sources is that Forteo and Tymlos have not appeared to be causing any cancer issues in clinical use. There was some concern for certain types of cancer in rodent students. I believe I just heard on a talk one doctor saying he was using both of them without cancer concerns.
And Evenity has no cancer related concerns from clinical results or rodent studies.
At -4.2 Tscore he is definitely in the bone loss range where you need to build bone before using a bisphosphonate which will not bring about a great deal of bone density gains.

@grrranny the black box warning has been removed from Forteo and Tymlos. Not a single case of bone sarcoma and Forteo has been used a long time. For Forteo the two year limit has also been lifted and Tymlos no doubt will follow.

I had breast cancer and that often metastasizes to the bones. I had no concerns doing Tymlos and am now done and no cancer!