I got John B. Blooms date of death from the York Chapel Graveyard booklet that was compiled by the late Anne Blanche Rutledge. If you can get to Perry County, you should go the graveyard and look at the stone again. Ms. Rutledge may have copied that year down wrong or maybe there was typo when the booklet was printed. You can also ask the Perry County Historical Society to look at their probate index and see if they a probate record on John Bloom and if so what year (I don't know if they will actually look up the probate record for you. The last time I asked them to do this, they said they did not have the "man power" to do it). The year it began probate would be the same as the year he died.
If the year is correct there are three other theories. One, Mrs. Bloom conceived right around the time of her husband's death and she was overdue (It's a little over 43 weeks from the time of his death to Emily "Jr."'s birth. And if I remember my biology correctly, human pregnancies are usually about 40 weeks). Two, Mrs. Bloom did not mourn the death of her husband too long and Emily "Jr." is actually illegitimate. Three, Emily "Jr." is actually an orphaned niece or cousin. There are no other Blooms in Perry County in 1850 and 1860 Census records. Therefore, if this correct her parents could have come to Perry County, had her and died all in between Census years or lived in a nearby county.
If I get to the library soon, I will check out Cape Girardeau County. I only have Perry County books at my house (that's the only society I have joined so far). If I find anything out, I'll let you know.