Ben Sira was a matter of dispute in the Talmud if it may be studied.
Rebbi Akiva includes in the Mishna's list of those who have no portion in the world to come (Sanhedrin 90a)
ר"ע אומר אף הקורא בספרים חיצוניים
Also someone who reads external books
The Gemara (100b) quotes the opinion of Rav Yosef:
בספר בן סירא נמי אסור למיקרי
It is also forbidden to read Ben Sira
Abaye then questions what about the works of Ben Sira is objectionable, and cites a long list of possibly objectionable teachings of Ben Sira, all of which he finds parallel to in words of Chazal, until he finally finds a statement which is objectionable - Rashi explains the objection as follows (s.v. לא יכלי ליה)
וכל הני דברי רוח
This is all nonsense
The Gemara concludes with the statement of Rav Yosef:
מילי מעלייתא דאית ביה דרשינן להו
The positive ideas in it, we expound
on which Rashi comments (s.v. דרשינן)
כלומר אמרינן להו בפרקא ומשמעינן להו לכולי עלמא
Meaning, we say them in public discourse and teach them to the public
From this discussion, it seems that even Abaye, in his defense of the book of Ben Sira, is only because of external validation of it's ideas. By implication,however, he finds all of the other ideas valid, and therefore one could draw on them. Rav Yosef seems to maintain that there are objectionable ideas in the book, but if you happen to know which ones are valuable ideas, you can teach them.
The Talmud does cite Ben Sira in various places (ex. Chagiga 13a), seemingly validating it, however those could conform to Rav Yosef's conclusion that if you know it you can teach it.
So as a reliable source of Jewish wisdom, it seems that it does not qualify.
As far as halacha is concerned, it would be difficult to imagine why it would be more independently reliable for halacha, and it is not explicitly quoted in Sha"s in a halachic discussion. Rashi in Eruvin 65a s.v. בצר אל יורה attributes a seemingly halachic statement to Ben Sira
אמר רב כל שאין דעתו מיושבת עליו אל יתפלל משום שנא' בצר אל יורה
Anyone who is unsettled should not pray, as it says "in sorrow do not shoot"
Rashi: ושמא בספר בן סירא הוא
Maybe this is in the book of Ben Sira
Tosefos offers alternative explanations of the source. However, this statement is not codified in halacha, and from context of the Gemara there it seems it may be more of good advice than a statement of halacha. Additionally, it happens to be that this sentiment is independently validated elsewhere - Berachos 31a:
ת"ר אין עומדין להתפלל לא מתוך עצבות
The Rabbis taught: one should not get up to pray in a state of sadness
and would therefore fit into the aforementioned rule of Rav Yosef.
So as a decider of halacha, it is at best tenuous.