Well it’s kinda been the dilema since the epistemological turn though hasn’t it. 
The absolute - I’ll agree - is beyond us. We’re subjects, we’re limited to a certain frame of reference - i.e. a subjective one - and any claim to absolute knowledge, with the exception of self-awareness and tautological tautologies (ho ho ho), is most likely faulty. The Kantian solution, for instance, which many feel reconciles empiricism and rationalism (or the external and internal worlds implied by dualism) makes a few unverifiable assumptions (the fact that synthetic a priori knowledge of spatiality and temporiality constitutes an infallible foundation on which to base a solid metaphysical framework), and thus doesn’t really go anyway to eliminating this ontological gap.
However, absolute skepticism - which suggests that just because something cannot be verified 100% that it should be dismissed as meaningless (a less severe version of which exists in logical positivism) - misses the point somewhat. I cannot prove to myself - to an absolute degree - that the world exists (much less to you or anyone else), but, as Neitzsche said, “another world is entirely undemonstrable”. I may not be “certain” of anything objective, but the reality perceive - the external world I walk about in - is a damn sight more demonstrable or verifiable than any other alternative. Sure, we could all be in a Matrix like situation where our brains are plugged into robots and we’re in a perpetual state of dreaming, never quite aware of “the real world”, but it’s a baseless assumption.
On the balance of probabilities - without wishing to devise a probability table to prove it to the rest of you in the same vain as Wittgenstein - I exist, you exist, the planet exists, the universe exists more or less as we see it. There is no infallible piece of rhetoric or mathematics to support this statement, but, on the balance of probabilities, it’s far more likely the scenario than any other.
By your “knowlegde” equation, I think my approach is workable anyway. If we assume that reality is one of two possibilities (to create a potentially misleading dichotemy) - the world exists as we perceive it or it doesn’t. Assume the first possibility - that the world exists as we perceive it - is actually objectively true (which is obviously undemonstrable from a subjective frame of reference) and that this possibility equals P. We are left with:
1) P is true
2) I (as S) believes P
3) I am justified in believing P (as all evidence available to me suggests as much)
P is verifiable from all but the most stringent form of logic. But the logic we’re talking about is self-defeating in a way anyway - does absolute skepticism hold-up when faced with absolute skepticism? How do we know that such a logic exists? Is it verifiable? Is it justified? Is it meaningful? Perhaps such skeptics an hold their logic up to itself, and see how whether it is workable. For a logic that isn’t internally self-consistent cannot be treated seriously.
So how about it then? Anyone wish to prove to me that absolute skepticism exists and/or is justifiably applied to the things that it is - using only such a logic? Does the strict logic it implies actually deny itself when it is applied to itself (in the sameway that the probability structured skepicism in logical positivism is self-defeating when it is analysed with its own principles)?
Just a thought.