Fortigate PPTP push default gateway and DNS server

I've got a fortigate 40C here and copied the config mainly from a Fortigate60.
Everything is working fine, but I've got some problems with the PPTP VPN connection. I want to add SSL VPN in the future, but for now PPTP is fine.

At the moment I got a working configuration, but some things are not working properly.

• the DNS server is not pushed to the client. It should be 192.168.6.1 like via DHCP.
• the client should use the gateway 192.168.6.1, not 192.168.160.1

I use the OS X VPN client to connect and I've added the dns entry + network settings manually, so it works.

Does anyone have an idea how to get the DNS + Gateway pushed properly to the client?

   config system dns
        set primary 8.8.8.8
        set secondary 8.8.4.4
        set domain "lan"
   end


config firewall address
       edit "all"
       next
       edit "Internal_Range"
           set subnet 192.168.6.0 255.255.255.0
       next
       edit "PPTP"
           set associated-interface "wan1"
           set type iprange
           set end-ip 192.168.6.180
           set start-ip 192.168.6.160
       next
   end
    config firewall policy
        edit 1
            set srcintf "internal"
            set dstintf "wan1"
            set srcaddr "all"
            set dstaddr "all"
            set action accept
            set schedule "always"
            set service "ANY"
            set nat enable
        next
        edit 50
            set srcintf "wan1"
            set dstintf "internal"
            set srcaddr "PPTP"
            set dstaddr "all"
            set action accept
            set schedule "always"
            set service "ANY"
        next
        edit 4
            set srcintf "wan1"
            set dstintf "wan1"
            set srcaddr "PPTP"
            set dstaddr "all"
            set action accept
            set schedule "always"
            set service "ANY"
            set nat enable
        next
    end
    config vpn pptp
        set status enable
        set eip 192.168.6.180
        set sip 192.168.6.160
        set usrgrp "Wizard_users"
    end
    config system dhcp server
        edit 1
            set default-gateway 192.168.6.1
            set domain "lan"
            set interface "internal"
            config ip-range
                edit 1
                    set end-ip 192.168.6.159
                    set start-ip 192.168.6.100
                next
            end
            set lease-time 345600
            set netmask 255.255.255.0
            set dns-server1 192.168.6.1
        next
    end
    config system interface
    edit "wan1"
        set vdom "root"
        set mode pppoe
        set allowaccess ping
        set type physical
        set alias "FTTB Fixed IP"
        set username "X@X"
        set password ENC X
        set defaultgw enable
        set dns-server-override disable
    next
    edit "modem"
        set vdom "root"
        set mode pppoe
        set type physical
    next
    edit "ssl.root"
        set vdom "root"
        set type tunnel
    next
    edit "internal"
        set vdom "root"
        set ip 192.168.6.1 255.255.255.0
        set allowaccess ping https ssh
        set type physical
        set alias "LAN"
    next
end

edit: The DNS server, the gateway are all on the Fortigate unit with the IP 192.168.6.1.