Some very good points you raise. No single one of them is to blame for your recent lack of catching. Considering you only spent about fifteen hours on “new to you” water, you are in the majority as far as catch rate is concerned. It would take much more band-width and time to adequately address all the points you listed, so here is a brief response to get you started.
Perhaps the biggest difference between where you used to fish, in the Far North, and here on Vancouver Island is the dearth of resident fish here. For the most part, salmonids here are mainly ocean going (anadromous). That means they get most of their food out in the salt water. On average, the interval they have for feeding while in freshwater is very limited. And that is mostly done by recovering steelhead and trout spawners and opportunistic Cutthroat trout coming in to feed on salmon eggs during the spawn. Then again, the exception proves the rule. Every now and then a nice trout will holdover in some preferred location and be able to eek out a living in the stream, but they are rare.
As a local example; the Puntledge river. That portion of the river between the impoundment dam at Comox lake and the diversion dam several kilometres downstream holds resident trout, as they have no easy way of getting back to the sea and the low flow velocity and low gradient makes for good bug/crayfish habitat. This is also a “fly fishing only” section of the river. The rest of the river, below the diversion dam, offers upstream and downstream access to salt water but is relatively sterile as far as trout food production goes. And, with the runs of steelhead to the Puntledge river system being in a depressed state, catching at this time of year could be described as “spotty” at best.
For a more consistent catch rate, if that is the motivation, try some little lakes as they have a captive supply of usually willing to bite fish. In between times, try getting back to the streams in search of that one holdover fish which could make your day. Remember; time spent fishing is not subtracted from one’s allotted span.