Setup DMZ into client's intranet network using M0n0wall

Question

Me and my team are sitting in a client's office. We're trying to setup our m0n0 that works like the following:

Interfaces:

1. rl0 - WAN - Uplink to 3G modem for our internet access. Set to DHCP as the modem itself is a router with DHCP running.
2. rl1 - LAN - Our network. Interface set to 192.168.1.1 and DHCP is enabled on this interface.
3. rl2 - OPT1/DMZ - Link to client's intranet network. No DHCP services enabled on client's network, we have set our IP address to 10.198.250.151 and I also manually added a tag because the client's switch will only accept packets for combinations of a specific IP and MAC address only. By design, I want to be able to route packets to all class A private network addresses through rl2.

Interface config looks like this:

   <interfaces>
      <lan>
         <if>rl1</if>
         <ipaddr>192.168.1.1</ipaddr>
         <subnet>24</subnet>
         <media/>
         <mediaopt/>
      </lan>
      <wan>
         <if>rl0</if>
         <media/>
         <mediaopt/>
         <spoofmac/>
         <ipaddr>dhcp</ipaddr>
         <dhcphostname/>
      </wan>
      <opt1>
         <if>rl2</if>
         <descr>DMZ</descr>
         <ipaddr>10.198.250.151</ipaddr>
         <spoofmac>00:1E:EC:72:ED:92</spoofmac>
         <subnet>16</subnet>
         <bridge/>
         <enable/>
      </opt1>
   </interfaces>

The static route looks like this:

   <staticroutes>
      <route>
         <interface>lan</interface>
         <network>10.0.0.0/8</network>
         <gateway>10.198.250.151</gateway>
         <descr>Route to client network</descr>
      </route>
   </staticroutes>

My problems right now:

I added a static route for 10.0.0.0/8 on LAN to route to 10.198.250.151. But nothing is being routed to the client network interface. Am I missing anything here?

After I added a couple of NAT rules to the DMZ interface, I've verified that inbound traffic from my client's network can hit m0n0 and also route through my servers sitting behind the LAN interface (with appropriate NAT and firewall rules put in place).

But I still can't get outbound traffic from my LAN to go into the DMZ network for some reason.

After I'm done with this, I will need to add one more feature. I need enable the VPN server and have it listening on the DMZ. The reason is 'cos somewhere on another floor, we have another team with a router. We want to establish a VPN between our two routers so that they can use our 3G line out. Is this possible?

Thanks for any answers! Wong