Hi, I hope this will help
1) At first please erase the default gateway command because you are doing routing and your default static route is configured. That is causing the problem.
#
conf t
no ip default-gateway 10.1.12.2
#
After that please erase from port 24 all the tagged vlans just maintain vlan 10 untag. That beause it is not a trunk (dot1q) is an L3 connection through the firewall.
2) There is no an exact place to configure the IP address to manage the stack. As I understand from your configuration VLAN 10 is your Management IT LAN so you have to configure an IP address from that VLAN on the switch. The way to do it is:
#Enter configuration mode
conf t
#Create an L3 interface (SVI)
interface vlan 10
#Configure an IP address to that SVI VLAN 10 interface
ip address 10.1.12.x 255.255.255.0
# Create a default gateway to your core via vlan 10
exit
ip default-gateway 10.1.12.1
After that you will access the VSF cluster management through that vlan 10 ip address.
Try and let me know if that helps.