That something can be technically done might be not even the best to realize it really.
So if I had to be true fully to you I would aware of such a set up like yours.
In service networks from TIER1,2,3 or smaller or locally homed ISPs this could be done
and is often offered as a service but based on totally other hardware devices and on top
of this surely based on faster and more stable connections or uplinks.
You as a company are using a customer network but this named above carriers or ISPs
are driving this through their service network and then it is more stable and on this stage
it makes sense.
I want when the QinQ connection is established,computer2 get the ip from the DHCP Pool on PF1.How can i do this?
QinQ VLANs are Layer2 based and the entire WAN through the Internet will be a routet way
so it could really be, that you will be having success with a L2TP/IPSec VPN connection or
a BGP connection betwenn this two points, but I personally would recommend the following.
Let the QinQ VLANs end at there WAN end point that might be the border firewall, border router
or a gateway at a network edge or node and than connect the both networks over one or more VPN
or BGP connections and thats it.