1) The Torah tells us a few Mitzvos which have to be performed in the Yovel year, and if they are not performed it is possible that the Yovel year does not apply. In fact, if one looks at Rashi at the top of Daf 9b, one sees that logic would dictate that if if one did not sound the Shofar and set free the slaves, then Yovel would not apply. It is only because there is an extra verse that says, "It is Yovel," that we learn that even if one did not do these things Yovel still takes effect. The Halachah does not follow Rashi, because he is referring to the Havah Amina of the Gemara. At any rate we do see the idea that the existence of Yovel depends on its special Mitzvos being performed.

2) Cancellation of debts has nothing to do with Yovel. It is a Mitzvah connected only with the Shemitah year. This is stated by the Rambam in Hilchos Shemitah v'Yovel 10:16: "The seventh year possesses something extra than Yovel because the seventh year cancels the debts while the Yovel year does not cancel the debts."

3) It appears from the Minchas Chinuch 335:2 that it is not the lack of the observance of Yovel that causes land not to be returned, but rather the opposite: if land is not returned, then automatically Yovel does not apply. The Minchas Chinuch writes that if no field returned in Yovel because nobody had bought a field from anyone else, then Yovel would not be in effect.

4) To summarize, the answer to your question is that we are not suspending a Torah law, but rather it is the opposite: the Torah states that if certain Mitzvos are not performed, then Yovel never applied in the first place.

Kol Tuv,

Dovid Bloom