I actually agree to a great extent!
Would like to clarify that I have no expectations that he should have singled out the EOC, and that in his public works, of course, one of his biggest goals was to avoid singling out the 'divisive' tenets of a given faith. This is both his great strength and great weakness, but he intended it that way. He said that his aim was not to distinguish between Christian religions, but to bring in people that were 'not inside the hall' at all (although conversely, a number of atheists have told me that they do not find Lewis convincing
).
So yes, Lewis was very orthodox, leading Bishop Kallistos (Ware) to say that he was Orthodox and didn't know it (capital O for EO only). His concepts of salvation and damnation, liturgical worship, etc etc are all quite Orthodox - compatible with Orthodoxy.
Lewis did make references in his
private writings that gave away some of his positions, though, so we have some hints, at least, as to why he did not become Catholic (despite the tremendous Catholic influences on his conversion) and why he was Anglican. That he did mention Catholicism repeatedly shows his awareness of the relative importance of the Catholic Church. So it's mainly disappointing that a huge portion of Christendom that had existed for 2,000 years (or if you are Catholic, 1,000 years after the GS) doesn't even get a mention in his non-public writings. Again, given his calling, he couldn't have not been interested in the development of his Church (and how it could claim to be Christ's Church sent into the world) prior to the Reformation.
As to theosis, Lewis was referring to all mortals as not 'mere'. Theosis is the Orthodox way of becoming like Christ, which only those who choose the difficult path of striving to be perfect as Christ said undertake, so the concepts are not identical. Those that undergo theosis would be the ones 'we are tempted to worship'. But I'm not a theologian, just a simple Orthodox guy, so if you want more accurate info go to oca.org or the antiochian or Greek (goarch) sites for online info straight from the horse's mouth.
http://www.antiochian.org/
http://www.goarch.org/
http://www.oca.org/
"Eh? Two views? There are a dozen views about everything until you know the answer. Then there's never more than one."
Bill "The Blizzard" Hingest - That Hideous Strength