I have not personally worked with the Shrewsoft client. But if there isn't a "route all traffic" option available, I often find changing the remote network definition to 0.0.0.0/0 will do the same thing.
You will need to change the corresponding VPN defintion on MFE so that the local network value is set to 0.0.0.0/0 also.
I have worked with some customer's who wanted to this with remote sites running the old McAfee UTM (SnapGear) Firewall to force all traffic over the VPN and this method worked for them.
Hope this helps.