I understand why someone would not want to come and go through the Straits unless they had to. It's a long day/night sail and can be rough and lots (as in lots) of big ships going and coming. Port Townsend and Anacortes on the US side are the ports
with the most boat parts
and services (by far). I think Sydney would be excellent. But all those are on the inside of the Straits. Port Angeles has some stuff but not as much and it is almost to the end too.
Gray's Harbor might be good but it is mostly a commercial
fisherman port and you won't find many of the parts
you might need. There may be very good basic boatyard services though.
I would recommend Astoria too. But, you have to get in through the notorious Columbia bar. I have done it twice and gone by it twice with absolutely no problems. But not everyone has been so fortunate. If you time the tides and weather
right you won't have a problem (and navigate the channel in right!). It's a cool town too. While it is several miles inland up the river, once you are across the bar it is much easier traveling than the Straits.
You can find some parts and stuff in Nootka but I don't think it offers the major services/parts you might need. If you only need some minor stuff you could try. You will go by there anyway. It's mostly smaller and commercial
Our shakedown cruise
(two months) was around Vancouver Island and it was our favorite cruise
of all time. Have fun.