Glaucoma with 30% optic nerve damage. No peripheral vision loss. For patient to notice peripheral vision loss, how much nerve damage must there be?

Variable. This depends upon the sensitivity of the nerves under the stress of the elevated pressure in the eye. Some will loss measurable amounts of vision at 30% damage, others require more loss to detect it. There is good adaptation so it takes a sensitive person to best detect loss. Best to get treatment and avoid any loss at all.
It depends.... There is no set answer to this. It is generally accepted that to develop a visual field defect about 30% nerve damage may need to occur. The reason that there is no straight answer to this is that it depends on: where the visual field defect occurs since both eyes work together, they compensate and the visual field defect may not be apparent.