https://lartc.org/ will help you. Exactly https://lartc.org/howto/lartc.rpdb.multiple-links.html In my same setup i was add some 'up ip rule add ...' lines into /etc/network/interfaces
I finally resolved the issue with the helps of your article and this one:
https://blog.scottlowe.org/2013/05/29/a-quick-introduction-to-linux-policy-routing/ Thanks a lot.
