What I mean is that if we assume that an idea is demonstrable, does this necessarly imply we assume it's open to possible refutations?

Don't think so.

If it contradicts reason, and that really implies logic, that is the ultimate refutation of any proposition.

From what I have heard/read him say, that is not completely surprising, altho it is a bit WTF? to have him so explicitly demonstrate just how his position is based on the most empty and ultimately dishonest form of theology, which does indeed require 'sophisticated' argument, in the worst sense of that word: convoluted enough to make it all but impossible to point out any simple error.

This sounds like he is into the sort of 'argument' which openly uses special versions of 'logic' and 'reason' which are only applicable to God.

He's certainly a very persuasive persona.  But personally more than a couple of times I've seen him get a bit full of himself, I studied philosophy in college so I know that claiming to be a philosopher is no guarantee that the arguments of a philosopher are necessarily better than that of a layman.

I haven't read up on him as much as I have Lee Strobel.  But from what I've seen of Lee, I think that WLC does many of the same things.  He constructs elaborate, hard to rebut arguments based around 'solid facts' like depending upon the claims that the Gospel writers were eyewitnesses (likely untrue) and that they would have 'died for a lie' if Christianity is false (also absurd, because such isn't based on history, but rather "Church Tradition", a collection of seemingly fabricated stories that can't be tied down with historical accounts).

The more you break down the argument to the point of the (often) unspoken premises that are frequently illusory, the less convincing WLC's arguments appear.  I'd have to see what claims he makes that can be proved scientifically.  That's historically been a very bad road to venture down for the theist.

Craig has debated some of the best atheists we have today. In my humble opinion, he has destroyed them all. He has over 30 years researching the fields of theology, philosophy, and cosmology, and christian apologetics.  As a christian apologist, he uses both scientitifc and philosophical reasons why theistism is more plausible than atheism. He is a genius, and in my opinion the best us christians have in apologetics.