Wohoo! Seahorses are awesome! And you have done the best thing possible by taking Pete's lessons!
Those lessons will cover pretty much everything you need to know!
However, i would strongly encourage you to buy your seahorses from a trusted site online. They will be much more interested in helping you if any problems arise, and then can guarantee that your horses are parasite free which can be a major problem. Also while the seahorses may look delicate they really are super tough so long as the conditions are good, and the people online have been shipping seahorses for year with no issues. Dont be afraid to order them online!
Also you really shouldnt rely on only feeding them live food, it should only be a treat. This is because if something happened to your live food stock, and each one will require around 6 shirmps per day, and they refuse to eat frozen you could be in trouble. Plus i dont know if you could culture enough live food in your sump to satisfy them, because you are going to want a herd of around 8 in that sized tank meaning you have to supply around 45 shrimps per day. I dont know of any type of shrimp that breeds that prolifically. Also enriched brine shrimp are not suitable meals for seahorses, only as an occasional treat. Also there is some species of seahorses, Reidi for excample, if they have too much access to live food like pods they may refuse to eat frozen. Just something to keep in mind.
I cant wait to see your build! Remember lots of hitching posts, they would LOVE a planted tank (im thinking of turning mine into one)