You REALLY don't like OpenVPN right? :P
Let's put this very simple:
If you want to be able to selectively route internet traffic through the link, **forget about IPsec ***
If you really want to use IPsec, you will be able to access the VPS and its subnet with no problems. Just create a regular Phase1, and then an appropriate Phase2 which links the subnets. Allow all traffic on the IPsec "interface" on the firewall rules, and you are done
Regards!
Disclaimer, just to be technically correct, hehe: actually you could route some internet traffic if you manage to know the certain IP address/ranges that those sites utilize, by creating a Phase2 on both firewalls, with that subnet. Even if you could do it, it will be waay too cumbersome for something that you can easily achieve with an OpenVPN tunnel