IME seahorses do not need to be kept in pairs, but they do interact with other seahorses.
They do not like temps around 74F, they NEED temperatures below 74 for long term survival. This has to do with a bacteria (vibrio) that they carry in an asymptomatic state. Temperatures above 74 allow the bacteria to alter it's protein structure and become much more virulent leaving the seahorse susceptible to disease.
Seahorses are not hard to keep at all, they just require a system that is setup for them. If you put them in a gold fish bowl they will die. Same as if you put an acropora in a goldfish bowl they would die. Seahorses have inefficient digestive systems so they require to be fed 2x a day, they don't break down their food well so many seahorse tanks have nutrient issues. You just have to plan for it. It is not difficult.
I also believe that seahorses do enjoy a higher rate of water movement, but the movement needs to be spread out, not in a narrower powerhead. My best success with seahorses have been in tanks with over a 50x return, usually accomplished by spraybars under the rock. This keeps the seahorses hunting around well, and it also helps to prevent the accumulation of uneaten food.
I would recommend a protein skimmer in a sump, but that is not NEEDED, just handy to have; especially if you choose to vodka/carbon dose the tank later to control nutrients.
They do require specialized care, but they are wonderful animals. Best of luck to you.
HTH