Learn English – “I came from Italy” or “I come from Italy”

My tendency is to use the present tense verbs when the subject I'm clarifying is currently present or would be expected to be present again. Likewise for the past tense; if I don't expect that subject to be present again, then I would prefer the past.

As an example, I would use "what is his name again" in cases where I'm talking about a friend I expect to see again, someone I met who is still at the same party, and so on. Conversely I would use "what was his name again" to talk about a salesman I'll never see again, a coworker that moved to tibet to be a monk, or other cases like that.

Put another way, my choice in normal speech becomes a reflection of the possibly unspoken current circumstances and future expectations surrounding the person or thing I'm inquiring about.

Can I just write "now it held", and it be obvious that now refers to "the point in the story currently being narrated" rather than "the point in time the reader is reading this point in the story"?

Absolutely - that is part of the craft of being a fiction writer. Although I would probably prefer the word order "But it now held just one woman.". Also a "single woman" sort of resonates in respect of whether she is married or not. There are good alternatives such as "a solitary inmate" or "a sole prisoner".