The premises you list seem to presume a priori that the object of our knowledge is our mind since our mind is the power by which we have an object of knowledge at all. If you start with that, it's hard to have a conclusion other than yours.
Yes, I think this is true.
But, if you are open to the idea that the object of our knowledge is really the external object, known THROUGH the mind, then it's easy to see that we really can know things beyond our own mind.
This is just the opposite metaphysical assumption, realism. What you're saying in this sentence is, if we accept realism, then it's easy to see realism is true.
Now, if one wants to play the hard skeptic he can probably always find some objection to the proposition that our mind really can touch reality so to speak.
I believe so grin, but I wouldn't assume that "reality" refers to something outside the mind in the first place.
However, that objection melts away at the long list of absurdities one has to hold if he thinks our knowledge only self-references the mind.
I honestly believe that asserting the existence of matter is more absurd than my view. It's absurd to assert a thing which lacks any describable qualities exists. Furthermore, the idea that this mystery substance can inexplicably affect the mind is absurd. I know most people would see me as a weirdo for having this view, but I've never found any objection to it other than it being too weird for them. I believe that it's only weird because our culture teaches us from youth that matter is the default truth, when really the idea of matter is quite strange itself. We could have been raised to believe life is mental, and it's weird to believe in something which by definition can never be seen, felt, etc.
For instance, would that not mean that science is pointless,
Not at all. Science is a process of observing and making predictions about the natural world. The only difference is that we would no longer assume matter is part of the natural world.
literature is an exercise in futility
I don't see the connection.
and even that this very conversation is mental tapestry?
Yes, this conversation is entirely mental. It's awesome.