The consular date given in the law is certainly incorrect. Mommsen proposed an emendation: CONSTANTINO A. VI ET CONSTANTINO C., that is 320 but Constantine was not then in Constantinople (which was not yet called "Constantinople" in 320). Seeck proposed CONSTANTIO IIII ET CONSTANTE III AA, that is 346, the only possible consular date for Constantius II and Constans, when the emperor was in Constantinople.
The phrase "clericis ac iuvenibus" is unclear. Mommsen proposed to correct it "clericis senioribus ac iuvenibus" and compared it with a Greek phrase "πρεσβύτεροι καὶ διάκονοι". Delmaire (2005: 130) proposes that the word "iuvenes" refers here to young boys serving as lower clerics (e.g. lectors). Faivre (1977: 284-85) it might refer to fossores.
On the menial duties in Delmaire 2005: 138-139.