Yes, 17 is the max on the north side, plus the two that spawn on the south side. I typically go in on 16.I have found that if you go in and out 10 or 12 times you can get up to 17 spawn points. This is the max. Yes, this is a very good place for harvesting talismans.
I'd say that it yields at least one gold talisman on about half the runs, and you get a pretty good percentage of multiple gold talismans.
Grand talismans are rare, but they do come, and the rate has increased for v65 vs v63.
Others have said that they've farmed royal talismans, but I haven't. I've dug only one out of the ground, which I suspect relates to the crafting recipe necessary to the story-line.