Re the Oak Street/Hobart Blvd house:
PREPARE TO HAVE YOUR MIND BLOWN, ER + SOME NOIR
When looking into the house at the nec of Oak/Hobart and Fountain, I took a look at the GSV of the its later address on Fountain (5287/89) and dismissed the building now there as a replacement, even though I didn't see a demo BP when I looked into those. But then I looked a little closer...
Notice the little west-side bay near the front--it corresponds to the bay indicated on the 1919 an 1950 Sanborns. So it seems your mystery house stands!
Among the changes to the house made over the years was its being was stuccoed over in 1984...
And, of course, into every LA house creeps a little noir...
LAT Nov 24, 1943
I couldn't find anything more of Irene Seidcheck (other than that her brother-in-law died in 1964)