The spark is ok.
I will return to the cabin in 1-2 weeks and will give you compressed air suggestion a try.
You mention that it takes some "mechanical skill" to get at the parts. Could you explain in more detail what you mean by that? There seems to be a hole/opening at the bottom of the inside unit where the pilot light and ignition spark can be viewed through a small round viewing window.
How do I find the way to rate the service?