I am seeking advice on constructing headings for Catholic Church synods.

Some examples of works I am cataloging:

Decreta edita, et promulgata in synodo diocesana prima Mediolanensi (first diocesan synod, 1568)
Decreta edita, et promulgata in synhodo dioecesana Mediolanensi habita anno MDLXXII (1572)
Synodus dioecesana Mediolanensis trigesimaprima (31st, 1629)

A sampling of authorized (RDA) headings in OCLC show several different ways to approach these types of headings:

n 2014213769:    Catholic Church. ǂb Archdiocese of Goa and Daman. ǂb Diocesan Synod ǂd (2002 : ǂc Pastoral Institute St. Pius X)
n 88208772:        Catholic Church. ǂb Diocese of Barcelona (Spain). ǂb Synod (1860)
n 94021506:        Catholic Church. ǂb Archdiocese of Manila (Philippines). ǂb Sínodo ǂd (1582)
n 2012062668:    Catholic Church. ǂb Diocese of Adria-Rovigo. ǂb Synod ǂn (28th : ǂd 2008-2011 : ǂc Adria, Italy)
no2009010508:     Catholic Church. ǂb Synodus provincialis Ruthenorum ǂd (1720 : ǂc Zamość, Poland)

From the above examples, I am wondering:

Do I prefer "Synod" (according to RDA 11.2.2.27), or "Diocesan Synod", or "Sinodo", or "Synodus diocesana Mediolanensi"?
Is the date in a separate subfield or does is qualify the synod, as in the 2nd example "Synod (1568)"
Regarding numbers, dates, and places: if a work calls itself the 1st or 4th or 31st I should follow the "ǂn (nth : ǂd year)" model, but if it just indicates a year use "ǂd (year)"?
If it doesn't explicitly say it was held in Milan, leave out subfield c?

Following the examples above, I'm leaning towards:

110 2_ Catholic Church. ǂb Archdiocese of Milan (Italy). ǂb Synod ǂd (date)

Not all of the synods say 1st or 4th, etc.; the date seems to be point of difference in the works.

Many thanks in advance,
Chloe

Chloe Ottenhoff
Rare Book & Manuscript Library
University of Illinois at Urbana-Champaign