The 1930 census shows Frances 39 was a widow. Valeria is age 14 so she was born in 1898. Try as I might I could not find the family in the 1920 census at all.
At familysearch.org under PA county marriages it shows the widowed Frances Gaca, born Sept 8, 1891 in Poland, remarrying to Mike F. Halesisk in 1941 in Pittsburgh. The record indicates her first husband died in 1925. Her parents are listed as Stephen and Frances Ruda.
Try as I might I could not find Alexander and Frances' marriage record. It could be the database just doesn't have all the marriage records from Allegheny County.
If you know what cemetery they are buried in I suggest contacting it to find what they have in their records. If you know what church they belonged to check with them to see what they have on the Alexander and Frances in their records. If you don't know which church (assuming they were Roman Catholic) check with the Pittsburgh Archdiocese Archives to see if they can help you.
You could also try the Western Pennsylvania Genealogical Society to see if they can help you.
The indexes for Pennsylvania death certificates can be found on the PA Dept of Health website. If you get their death certificates they should give you much of what you are looking for.