While Boian was destroyed during World War I, civil transcripts of church records have survived. I can only surmise that these records were already archived in a regional diocese office or perhaps somewhere in Cernăuţi prior to the attacks on the village.
Metrical books (Orthodox church records of births, marriages and deaths) for the village of Bojan, Bukowina, Austria; later Boian, Cernăuţi, Romania; now Boian, Novoselyts'kyi raion, Chernivets'ka oblast, Ukraine, are available on microfilm from the Family History Centre of the Church of Jesus Christ of Latter-Day Saints (LDS, also known as the Mormons).
There are a total of 13 microfilms that cover the period from 1840 to 1944. This should give you several generations of information related to your Toma, Tkachuk, and other ancestral families. In addition, there are family lists covering the period from 1920 to 1944. This will give you insight into which families returned to the village after the devastation of WW I.
The microfilms are available for viewing at a nominal rental (about $7.50 per reel) for a 90-day loan period. You can order them online and have them delivered to your local LDS Family History Centre, or in some major cities, at your public library.
To locate an LDS Family History Centre near you, visit: https://www.familysearch.org/locations
. To register for a Family Search account to order your microfilms, visit: https://ident.familysearch.org/cis-web/pages/registration/re...
. To order your microfilms online, visit: https://www.familysearch.org/films/
Here is the link that contains more detailed information on the Boian Orthodox microfilms: https://familysearch.org/search/catalog/show?uri=http%3A%2F%...
. For an excellent article on the content and layout of the church records in Bukovina, visit: https://www.familysearch.org/learn/wiki/en/Bukovina_Church_R...
I assumed that your ancestral family was Orthodox. If they were Roman Catholic, microfilm information can be found at: https://familysearch.org/search/catalog/show?uri=http%3A%2F%...
. If they were Greek Catholic, very limited microfilm information can be found at: https://familysearch.org/search/catalog/show?uri=http%3A%2F%...
Good luck in your search!