there are a few details that are... off regarding this character. first of all "improved power" is a quality, not a virtue, and can only be taken bay a character with magical might.
also while I can see the idea of sidhe representing Olympians in that they tend to focus on the roles of rulership, the fact is there are a lot of established rules that define what someone who is a descendant of zeus would have- namely a sympathy trait with thunder and lightning, kings, or the sky. the mixing and matching of faerie and magic to try and wedge in a different definition just doesn't feel right
Finally the focus in thresholds to be minor would be limited to entrances/exits and the edges of auras/regios
Improved powers is a minor virtue (faeries, page 56 bottom of first column) even if it can be simulated by taking a second lesser power and converting the levels to improvement points. 2 ways to achieve the same result.
He is a descendant of Hermes not Zeus (or thinks he is). 
If this doesn't feel right I will just switch to magic blood and take a Delusion about his parenthood. I will think about his minor focus. Suggestions are welcome.
You could take Mythic Blood: Hermes Trismegistus, and he just is a descendant of Hermes, not delusional at all. Not sure if that's too much of a change in direction but it occurred to me so thought I'd share.
(I suppose his level of delusion depends on what the actual nature of Hermes Trismegistus is, I don't think there's a concrete canon answer but I haven't looked too hard; I've always assumed he was Hermes/Thoth in human form, but not actually human.)
OK,
Took mythic blood. I made his blood unknown. It can be a self-driven story hook, but he thinks he is a son of Hermes and hence a pseudo-Olympic returned to Earth because he can move really fast. It is a logic fallacy, but who cares? 
He is probably dragon blooded if he is an unwilling descendant of Bulgarians, but who knows? His mother is telling a different story about his conception after all.
The rest remains equal. I kept puissant stealth since it fits with his "Olympic Hermes" delusion (puissant MT would have been more useful).
by my count you have 9 points in virtues if you want to add puissant magic theory as well...
The last version of Isaac has 9 virtues and 9 flaws (3 major, plus 1 that comes from mythic blood). The only thing that makes me wonder is the magic focus.
I can approve it as is or you can put in a minor overconfident and an affinity or puissant magic theory as well- your choice.
I thought I had replied...
The character is fine as it is without more V&F. Fire way
after being recruited as Thermakopolis, Isaac will remian there 1 season with a tutor who provides him 14 points in ancient Greek before being sent to Polyaigos. At polyaigos he will spend the winter being tutored in ancient Greek with SQ:15. he will have chores in the spring and fall, and will be taught ancient Greek in the summer of 1192. he will receive another class in ancient Greek in the fall of 1192, then spend the winter learning order of Hermes lore with SQ:15. The spring will be a class in philosophae (still SQ:15), and summer 1193 you head to the tribunal. Keep in mind that classes may have points diverted to either ancient Greek or teaching, or when you are learning ancient Greek either teaching or artes liberales- up to 1/2 of the SQ (round down) per season.
Great.
Does Isaac get 2 exposure points per season as well or are they included in the total Quality?
yes, he will get the 2 point exposure.
Ok, XP for those 6 seasons:
- Ancient Greek 50
- Artes Liberales 10
- Teaching 5
- OoH Lore 15
- Magic Lore 1
- Folk Ken 5
I took a single point of Magic Lore as exposure because of the setting. Folk ken as Isaac explores how people react to him and meets new characters. Hope it is OK.
all good, just don't forget to note he is now 8 on his character sheet.
following the tribunal, Diogenes opens your arts, spends a season teaching you magic theory (SQ:14) then takes off for parts unknown (season of free study, potential SQ:7 for area lore: thebes), followed by 2 seasons of training in magic theory (SQ:9) as he sets up his lab in a new location, then a season of teaching you rego with SQ:14, and three seasons as lab assistant in a PeAn lab. he then teaches animal with SQ:14, then another season of travel (again free study with potential SQ:7 for area lore:theban tribunal), after which he spends the next two seasons setting up the lab for his parens, then assists in a reVi lab before being taught vim (SQ:14), before two more seasons of ReVi labs before you are taught finesse (SQ:14), and during the next season of travel there is an adventure...