ospf is a protocol, not a sys services: so this line:
set security zones security-zone VPN interfaces st0.2 host-inbound-traffic system-services all
is not enough. You also need set security zones security-zone VPN interfaces st0.2 host-inbound-traffic protocols all.
set security zones security-zone VPN interfaces st0.2 host-inbound-traffic system-services all
is not enough. You also need set security zones security-zone VPN interfaces st0.2 host-inbound-traffic protocols all.