here is the short and sharp...
1) through Yeshua.
2) Yes, keeping the full commandment of the law perfectly... but we
cannot so the only way for us is Yeshua
3) yes, when Shaul preached the gospel, they only had the OT to
refer to to ascertain the validity of his teachings, likewise, all
that we know from the NT is related to the OT. To us it is the OT,
to the Jews, it is their history. Then is buddhism verifiable?