What is the deeper signficance of the three stories about Rabbi Yossi from Yukra. The death of his son for producing fruit on the fig tree, the daughter who was beautiful and the donkey. It seem for a very harsh characterization of a very great Rabbi. I believe it is more than just stringency of Rabbi Yossi that sets a high standard. Please address this issue from a deeper perspective as to what one should learn from these stories.
the stories on how rav yosi treated his son and daughter are extremely difficult to understand -- can you shed some light on these?
The incidents that the Gemara records concerning the strictness of Rebbi Yosi of Yukras are indeed very difficult for us to understand. It is just worthwhile to point out that in the incident regarding his son, the Gemara does not say that his son actually died as a result of the curse (perhaps it would be hypocritical if he did: Rebbi Yosi rebuked his son by saying, "You were Matri'ach your Creator to bring forth fruits before their time, so, too, you should be gathered in [to your final resting place] before your time." If Rebbi Yosi really intended for his son to die early, then Rebbi Yosi himself would be Matri'ach his Creator to cause something natural to happen supernaturally before its time!).
In the case of his daughter, though, the Gemara does say that "so happened to her [that she died]" (however, these words do not appear in some manuscripts; see the Girsa of the Ein Yakov and the Dikdukei Sofrim). Moreover, it does not necessarily mean that she died; perhaps he meant that her beauty should return to that of dirt (as we find that ugliness is referred to as "darkness," the color of dirt, as we find on the bottom of 23b; see MAHARSHA).
Both incidents are emphasizing (1) the severity of demanding from Hash-m that He make any change in the natural order, since the natural order is so perfectly precise and in itself a miracle, and to demand a change in that order is to counter the will of Hash-m that He has for the way that the world should operate (SICHOS MUSAR of Rav Chaim Shmulevitz, zt'l, 5733 #8), and (2) the severity of causing others pain.
(See more regarding the incident of his daughter in "Tov Re'iyah," (by Harav Avraham Yitzchak Hakohen Kook zt'l) cited by Rav Yosef Ben-Arza in "Yosef Da'as." The Tov Re'iyah points out that Rebbi Yosi, and his daughter, understood that it would be a special Zechus for the daughter, and her purpose for being created, to die in order to prevent others from sinning because of her.)