I'd say pick up the speed if want to catch Coho. The gps is telling you your speed over land not the water you are in. I would watch the dr cables and try to get them to almost 45 with the tide. A lot of guys I know who slam the fish don't ever look at speed...just the cables.
I may have read it wrong but I thought you wrote you were using a flasher with a squid AND a cutplug? I may have misread that. I'd use the flasher/squid combo or flasher/coho killer or a straight spoon or a straight cut plug.
Just my two cents. Keep trying you will catch fish!
ps Port Madison,Apple Tree,W. Point,Meadow Pt. and Edmonds can all be great when the Silvers really start to come in. On some days they all produce well and others one or two of them are producing well while the others aren't.