What exactly were the "innovations" introduce in the Diocese of Chelm? There is always a tendency to assume that the Orthodox usage was correct and the Greek Catholic usage incorrect but that is not always true. I think we would need to have a good knowledge of the specific liturgical issues in order to put this document in context. My read of this is that the liturgical issues (serious as they were) were but a symptom of larger issues in the diocese at that time.

In principle Greek-Catholics retain the Eastern Orthodox tradition in matters of spirituality, theology, liturgy and discipline, but in practice the Greek-Catholic Churches have usually been severely romanised or 'latinised' in each of these areas. The Greek-Catholics in the Kholm diocese had endured a heavy dose of this 'latinisation'. By the middle of the nineteenth century the churches did not have iconscreens; the altar tables were fixed to the wall (which makes the processions and incensations that are necessary for the Byzantine liturgical tradition impossible); numerous Roman Catholic devotional practices and liturgical furnishings had been introduced everywhere; and the liturgical texts had been seriously altered in a romanising direction. The churches were furnished with organs, confessionals, and monstrances; various Roman Catholic devotions such as the feast of Corpus Christi, the blessing of fire, the Holy Hour, the Rosary, and the Stations of the Cross were in common use. The Greek-Catholic priests dressed and groomed themselves like Roman Catholic clergy. By the latter part of the nineteenth century the Greek-Catholics in the Kholm diocese had lost even the memory of much of their own authentic Orthodox tradition.

We ask of you only those things that are strictly necessary: return to unity; agree with us in the profession of the true faith that the Catholic Church holds and teaches; and, along with that of the whole Church itself, maintain communion with the supreme see of Peter. With respect to your sacred rites, only those things found in them contrary to catholic faith and unity are subject to correction. Once remedied in this regard, your ancient Eastern liturgies will remain unchanged.

Here is a convenient on-line source: Religion and nationality in Western Ukraine: the Greek Catholic Church and Ruthenian National Movement in Galicia, 1867-1900 By John-Paul Himka ( link )

Starting at page 42, The Conflict in Przemysl, but see especially page 57 The Conversion of the Chlem Eparchy to Orthodoxy.

It could also be that many of the "purifications" represented russifications; i.e., imposition of a Nikonian liturgy in place of the pre-Nikonian rite used by the "Ruteni". But without additional information, it is impossible to tell.