Deneb, I myself have epilepsy and have found stones in addition to the ones you list that have a connection to epilepsy. Since this is magic and not science, only you can know if they work or not for you. But before I give you what I have found, have you or your dad ever considered a Vagus Nerve Stimulator? It is sort of a pacemaker for the brain, it sends a pulse of electricity through the Vagus nerve to the brain to keep it on a steady beat. I myself just had one put in last December and it has been a big help in controlling my seizures. Ask the neurologist about it.
Now, on to the stones that may be a bit of help reinforcing the meds too. Hope this helps.
Emerald has long been a stone believed to aid epileptics. Emerald lore and tradition is older than recorded history so no one really knows where any of it started. Even though no one knows where the belief that the emerald can cure epilepsy began, I was able to find two recordings from the line of its history. Paracelsus's younger contemporary Georg Agricola stated that the emerald fights with epilepsy as with a deadly enemy. If the stone is stronger than the disease, the stone remains whole; if, however, it is conquered by the disease, it is broken into several parts. It was often worn as an amulet or ring for this reason, particularly by children. Anselmes de Boot, a seventeenth century philosopher, was another who recorded that it prevented epilepsy.
The fumes Jet gives off when burned were once thought to have medicinal powers, able to cure hysteria and diagnose and treat epilepsy. This was because of the connection Jet was believed to have with the moon. People once believed that the moon was the causer of lunacy and seizures.
Because of its high sulfur content Lapis Lazuli powder was used medically for treating epilepsy in the 1600s.
A gathering of coral, peony, and the root of strychnos at the time of the waning moon, putting them into a piece of linen and hanging them around the neck was said to magically cure epilepsy. The reasoning for this was Coral's connection to water and the curative power of the dead.
In the Indian subcontinent, during the bygone ages, the inhabitants called Jade the 'Divine Stone' and credited it with being a cure for asthma, gravel, epilepsy and heartburn.
Topaz is another stone said to avert epilepsy, but I could not find much background info about why.
Jasper is said to prevent fever and dropsy, strengthen the brain, and promote eloquence; it is a preservative against defluxions, the nightmare, and epilepsy.
In Ancient Egypt Malachite was revered as the Great Healing Stone. It is said to promote complete tissue regeneration at the cellular level, by aligning the etheric and emotional energy bodies.
In all cultures, it is considered a symbol of the Goddess, be it Hathor, Aphrodite, Venus, or Freya as Malachite is known to alleviate menstrual problems and eases labor.
Right-left imbalance of the brain such as autism, dyslexia, epilepsy, coordination disorders and certain visual problems may be helped by Malachite's balanced energies.
I myself wear a Malachite ring and I feel it does help. Whether it does so medically, magically, or just emotionally, I can't be sure. So, of these stones and the one's you listed, I would say either Emerald or Malachite. Emerald has the most history behind it, but since Emerald is pretty expensive, I would go with Malachite. Malachite is said to balance the brain like Sugilite is said to and it has the green power of Emerald. Investigating the Vagus Nerve Stimulator might not be a bad way to go too.
Best of luck,
BlueManticore