The problem with defining knowledge as a justified, true belief (besides the Gettier thing), seems to me to be that we can never know that something is a true belief.
Even our most fundamental 'knowledge' about this world is subject to review. We once considered "the world is flat" to be knowledge, but we now know that this statement doesn't even fulfill the most basic requirements you set forth - truthfulness.
I would simply define knowledge as a belief which is justified beyond reasonable doubt - that's as good as you will ever get. You need to be willing to accept that human knowledge is not necessarily truthful.
Having said that, I can now reiterate: you are using a strange definition of 'knowledge'. If we think, we obviously exist. This belief can be considered knowledge, because it is justified beyond reasonable doubt.
As for Fundamentalism vs. Coherentism, though I've never heard of either before I will venture to say that the latter seems the most promising to me. All of our knowledge, according to the definition I have put forth, is dependent on our ability to doubt - this, in turn, depends on our expectations. Our expectations are an emergent property of all of our past experiences and current beliefs/knowledge - the whole system must support itself.