Not sure about the mobile service–I’ve also found it to be sketchy in some places. Also I tend to rely more on VHF radio for emergencies as I keep the radio in a PFD pocket.
Your route is very pretty, especially Cabbage Island but warning–it can become party central for local kids so hopefully you are doing this midweek. Be mindful of the currents going around East Point. There is a good reason for one of the features there being called Boiling Reef.
Narvaez is a very sheltered campsite–not much view but you’ll see it all coming and going. The south side of Saturna has spectacular cliffs and there is a winery on Saturna which is a good place to stop for lunch on your way back to Bennett Bay, if it is open. Good to be going with the tide on your way back, but not as testy as East Point.