I love skimmers, if there is anything I would wish everyone had, was a skimmer, followed closely by a UV.
Live rock is ok, but there are many sad stories of major problems with live rock, I prefer to see people wanting a seahorse tank to start with ded or base rock and seed it so as to make it live, very easy, very clean, no nasty surprises.
You will be surprised at how much flow seahorses can take, 4-5 times turnover is ok, but up from that is fine, fact is its better, just use a difuser so as to make the flow more even across the tank.
Ded spots are the bane of an aquarists life, they are to be activly sought out and eliminated, this can be done by directing flow, or by air from a open air line, that the horses will love, or an airlift, very simple.
I do love external canister filters, they IMO are a must, they work as both a biological and mechanical filter.
HTH