"Well then explain what you mean, then. You asked me for verses that show the cross is asolutely the only way to heaven."
the cross is, absolutely, the only way to heaven. But you do not get to define what the cross is, at least not for me, because Scripture allows that you might define it "Jesus died for your sins, and all you have to do is agree with us--verbally; you don't really have to
do anything

--that that is true, and you are going to heaven" when that is patently not true.
"Love one another"
is the doctrine, and anything you subordinate to that is a false doctrine, to answer the rest. You seek to "lay again the foundation."
Therefore, leaving the elementary message about the Messiah, let us go on to maturity, not laying again the foundation of repentance from dead works, faith in God,