Putting pedal to the metal
The form of scoring (IMPs, although 6-board club Swiss) and the vulnerability (we were vul) made it easy to put the pedal to the metal and drive to game on these two hands.
Yes, the failure of North to overcall 1♠ seems odd to me, too, but would not have changed the overall auction, with a negative double being substituted for the 1♥ response, and, presumptively, clubs being supported later over a spade raise advance by South. +600, with +100 at our teammates table for defeating 3NT on a spade lead. 12 IMPs our direction.
The heart lead made matters scary — well, I guess they could have been scary after a spade lead, too — but when clubs behaved, we scored up +600 (actually, +630 given lucky stiff ♦K). Teammates were -150 (probably defending clubs, although I am not sure) for a pickup of 10 additional IMPs.
IMPs is all about bidding your games — good job!