While is is true that this town was known by many names (according to this source), there can be little doubt that the family used , Kristianpoller. See, for example, the title page of this dirge which R. Yechiel Michl wrote for the death of Kayser Franz I. (You can read it here. Oddly, it is bound - or at least the pdf is included with - the 1809 edition of the letters of the Rashba.)
Similarly, you can see how he spelled his name in this letter included in Hirsch Edelmann's biography of Saul Wahl, Poland's Jewish "king for a day."
It's interesting, if not somewhat suspicious, how the name is spelled in Rabbi Meir Wunder's אנציקלופדיה לחכמי גליציה (Vol. 4. Column 618).
קריסנפולר instead of קריסטיאנפאללער or some modern Hebrew variant of it. There's even a bit of a discussion about the spelling here. I'm not going to be so quick to assume that an attempt was made to cover up the name, because the following does appear in Vol. 2 of Rabbi Wunder's Encyclopedia:
This could be the result of a clash of sources. Another example of the name spelled קריסנפולר can be seen here.
In any case, there can be no question that this surname is surprising. As I have shown before in some circles there was a reluctance to use + as a plus sign. Here's an example of a math book from 1829 which uses an inverted kometz for a plus sign, as it explains here:
I can't say for sure that it is out of reluctance to use a regular + symbol, but it seems likely. In one of the missionary journals I recall reading about a tumult that was caused by the footnote symbols used in a Hebrew Tanach which the missionaries were distributing, as was their custom. Often Jews were happy to receive such a free gift which ostensibly came without conditions. (The missionaries felt that there was value in the Jews having a Tanach unmediated with rabbinic interpretations, thus no Onkelos, Rashi, etc.) However, in this case the people were very disturbed that one of the symbols was a cross.
In any case, whether or not it can be argued that the name is similar or different, it seems a little odd (and, I might add, whether or not the name of the town technically means what it sounds like).
Leopold Zunz also knew it was odd, so he made mention of it in his 1837 book Namen der Juden. Namen der Juden was written to counter a Prussian decree banning Jews from using German names. So Zunz investigated the history of Jewish naming practices and showed that the Jews continuously adopted the names - including German ones - from the surrounding culture. (What do you think "Zalman" is?) Conversely, loads of "German" names were actually Jewish names, being derived from the Bible. It worked; the decree was modified to only forbid specifically Christian names. Thus Jews were allowed to continue to call themselves Heinrich, if they wanted to, but not Peter. On pg. 124-5 of his book, Zunz concludes with a passionate defense of a parent's right to name children as they see fit. He says that this is not a religious issue, as Christians can name their children highly religious Christian names if they want (such as Dodjeschu (דודישו), which he points out is a Syriac Christian name, or Christbold and the like). But is a Jew going to name their child Christlieb? Such names would be very, very unusual. So nothing to worry about, from a Christian perspective. "Christian" is a less distinctively Christian name (from a religious point of view) and it is rare among Jews. Here Zunz mentions 'the living "Rabbiner zu Brody,"' that is, R. Yechiel Michel Kristianpoller. Note though that he does not mention his name.
In 1843 a book about the Galician Jews called Galizisch-jüdische Zustände appeared anonymously, but obviously written by a Jew (he quotes Baba Bathra 89b, אוי לי אם אומר אוי לי אם לא אומר, on the title page). Writing about the rabbi of Brody, the author says:
At the top of the spiritual hierarchy [in Brody] is the honorable rabbi Herr Michel Kristianpoller, a man of justice and truth. His noble virtues, dignified demeanor, his impeccable reputation for deep Talmudic erudition, make him a man loved by the people. His bright views on the issues of life, his sharp attention to the conditions of his environment, his openly expressed tolerance for people of different religious viewpoints, his gratitude to people, make him a man of the time. He was almost unanimously elected to his position [av beth din] after the death of his predecessor, the revered rabbi Herr Lazarus Landau.
The author footnotes his name, and says
I must criticize a little mistake in Dr. Zunz's work on the origin of Jewish names. The doctor studied the widely-held misimpression concerning the Germanization of Jewish names, even proving the remarkable fact that the rabbi of Brody uses the name "Christian." The Galician Jews are not so culturally advanced. The first name of the rabbi is Michel. The surname "Kristianpoller" is merely the town, Krystianpol, where the rabbi's family comes from.
In any case, R. Michel Kristianpoller's daughter Breindel married Nathan Kallir (1821-1866), a man who eventually would be knighted (and known as Nathan Ritter von Kallir) and became the first Jewish member of the Austrian parliament. She was renowned for being very very pious. Him, observant, but less pious. In fact, according to this memoir (dictated in 1929), Breindele Kristianpoller Kallir was known as a tzadekes and her grave was a site of pilgrimage and prayer. The story goes that she was concerned that her husband should put on his tallis and tefillin every day. But as a very busy man constantly traveling to Vienna, without deep piety, she felt that he needed coaxing. One time she packed his clothes, but he could not find his woolen underwear which he would need as it was winter. He wrote back to his wife asking her where she packed it. Her response: "Go pray to God and you'll have your prayer answered." He understood: he opened his not-so-used tallis bag and found the underwear inside.
On that note, in the Artscroll book Aleppo City of Scholars a story is told of how the lack of piety of an Alliance Israélite Universelle school teacher was exposed when a piece of meat was put into his tallis bag. When it began to rot and the smell spread all over the school it was proved that he did not put on tefillin.
In the comments someone asked about "Satmar," which is allegedly "St. Mary." While most people now know that it doesn't mean that at all, the idea that it meant St. Mary is not something new. Many Jews called it "Sakmar," including the most famous Satmar Jew of all, R. Yoel Teitelbaum. See, e.g., this letter from him from 1934:
סאקמיר, not סאטמיר. You can do a search for both terms (and other spellings) at hebrewbooks.org and see many examples, both ways.
It also bears pointing out that Jews generally referred to "St. Petersburg" as "Peterburg" in Yiddish. One hears of "R. Itzele Peterburger," not "R. Itzele St. Peterburger." However, not too much can be made of such things, as in most cases the Yiddish names of cities and towns did not exactly match the name in the local language, particularly if there was a long history of Jewish settlement.