Your guesses are about right:.
The significance is that if rationalists respond to sceptical challenges by assuming what they can't prove, then they are then in the same position as reformed epistemology. That is, they can't say why their axioms are rational, and can't say why theists are irrational, because theists who follow RE are likewise taking the existence of God as something they are assuming because they can't prove it: rationalism becomes a label with little meaning.
So you're saying that taking a few background axioms that are pretty much required to reason... is equivalent to theism.
I think you may benefit from reading The Fallacy of Grey, as well as The Relativity of Wrong.
Standard methods of inferring knowledge about the world are based off premises that I don’t know the justifications for. Any justification (or a link to an article or book with one) for why these premises are true or should be assumed to be true would be appreciated.
Here are the premises:
“One has knowledge of one’s own percepts.” Percepts are often given epistemic privileges, meaning that they need no justification to be known, but I see no justification for giving them epistemic privileges. It seems like the dark side of epistemology to me.
“One’s reasoning is trustworthy.” If one’s reasoning is untrustworthy, then one’s evaluation of the trustworthiness of one’s reasoning can’t be trusted, so I don’t see how one could determine if one’s reasoning is correct. Why should one even consider one’s reasoning is correct to begin with? It seems like privileging the hypothesis, as there are many different ways one’s mind could work, and presumably only a very small proportion of possible minds would be remotely valid reasoners.
“One’s memories are true.” Though one’s memories of how the world works gives a consistent explanation of why one is perceiving one’s current percepts, a perhaps simpler explanation is that the percepts one are currently experiencing are the only percepts one has ever experienced, and one’s memories are false. This hypothesis is still simple, as one only needs to have a very small number of memories, as one can only think of a small number of memories at any one time, and the memory of having other memories could be false as well.