O house of David (comp. Isaiah 7:2). It is not Ahaz alone, but the "house of David," which is on its trial. Men are conspiring to remove it (Isaiah 7:6). If it will not be saved in God's way, it will have to be removed by God himself.
Is it a small thing for you to weary men? i.e. "Are you not content with wearying men; with disregarding all my warnings and so wearying me? Must you go further, and weary God" (or, "wear out his patience") "by rejecting his gracious offers?"
My God. In Isaiah 7:11 Isaiah had called Jehovah "thy God;" but as Ahaz, by rejecting God's offer, had rejected God, he speaks of him now as "my God."