Then you need to:

a) Add the 'optional' option on ppp0 and ppp1 in
/etc/shorewall/interfaces; and

Ok. I will see this. I think this is in that way. The problem was on tc_files who has defined ppp1 and ifb1. ppp1 was down and i think this was the problem. I will test this in a place without users.
b) Run LSM to handle up/down events.

I have LSM but i can`t make it work ok. I`m reading about this.
Once I have released 4.5.17, you probably want to install that and also
run Shorewall-init; it handles up events more quickly that LSM.

Ok. You say we will have a built in Link status Manager?

Best regards.