Candlesticks shouldn't be buildable, in my opinion. Rather a dwarf needing light would carry a lit candle around with them, and place them to light a room (place them as an item, not 'construct' them) - as it would be IRL. Continuing on this I would think a single slab of tallow to produce something in the vicinity of 50 candles, simply to feed the demand.
What I am getting at, is that due to the timescale we would need candles that last several days. Otherwise, dorfs would be carrying 20+ candles around with them or get nothing done. Otherwise, they'd spend all their time carrying candles to/from their workplace as they extinguish too quickly.
I see illumination as being the job of children, idlers, and/or a possible caretaker profession, whose other duties include things like Cleaning and relocating animals. It *is* possible to make candles so large that they burn all day. But yes, it'd be far more dwarfy to take advantage of natural cavern illumination (which, like Deboche, I presume will exist), such as transplanting bioluminescent fungus seedlings into stone pots, and then carrying the potted trees upstairs to use as streetlights. Etc.
And yes, Candle <> Candlestick. A
candle maker is/was a very viable profession, indeed there were chandleries pretty much everywhere, doing constant business. But a candle
stick maker was pretty much capped at something like 2 candlesticks per customer, with no repeat business, ever.