No somehow it stops prcessing IKE i tried to find something about it in open caveats but no success.

I have had that problem too upgrade too 7.2.(X) and it was solved.

I you connect them as stack, the switch will look like one STP ID. This means that you should look at it as one single switch. There will be no nead for HSRP because the switch is sharing MAC address for gateways. If primary fails Sec will still hold...