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.