help setting up VPN to use a gateway from my office

[Din Covo]

Hi all,

I have a 66U at my office with the latest merlin on it , i used to have another 66U at home with a VPN set up between the two (Server at workplace), to the 66U at home i have a simple router connected by cable and it was set with static ip address from the pool of my office(Through the vpn, using a gateway from the office as well), that allowed me to connect to a different ISP from what i have in my house through the office.

Sadly the 66U at the house died last week and i bought a 56S without know its not supported by merlin.
first it took some quite time i could set an openvpn connection because of the settings in the server required an open vpn 2.4 which is not supported by the 56S.

Now i do have the VPN running but it does not work the way it did before, i cannot just set my secondary router as if its part of the LAN and leech internet from the office's gateway.

DHCP on the the 66U & 56S as there is a DHCP running on my server, previously it would just assign any computer connecting to the LAN at the office but it just doesnt work anymore.

Here are the settings i use for the server:

would appreciate any help...