DHCP is fine, unless you're looking to perform advanced networking tasks. Here's how to set a Static IP address (or DHCP reservation) for any device on your network.

Here's how to set up DHCP reservations on your router so that each computer in your house has the same IP address all the time.

Looks like it's not "5 static IP addresses on 5 devices behind DSL modem in Bridge Mode", but 5 addresses behind PPPoE. If so, you need only one PPPoE connection on one of the routers (1), also ...

DHCP is fine, unless you're looking to perform advanced networking tasks. Here's how to set a Static IP address (or DHCP reservation) for any device on your network.