I have been using 7.5 with PPPoE but only on a single connection. MultiWAN is when you have more than one pipe to the internet. It is not apparent in your list of interfaces. I see one green (internal I presume) and one red (for PPPoE I presume). Could you clarify your current setup? Based on your opening statement, it seems that you are talking about a single connection using PPPoE.
I have 2 Internet channels (2 red interfaces)
eth1 (red1) - channel with dedicated IP
eth2 (red2 - pppo) adsl Internet.
eth0 (green) - local area network