Ok, 5 routable addresses means you’re getting subnet xxx.xxx.xxx.224/29 from ISP1 and … ugh, no subnet matches the addresses you mentioned by routable addresses from ISP2.
Since bridging between PPPoE and ether ports is not possible, you’ll have to configure RB for routing. For that you’ll need to configure one IP address to bridge (spanning ether ports towards pfSense).
Example for RB hooked to ISP1:
/ip address xxx.yyy.zzz.229/29 interface=bridge1 network=xxx.yyy.zzz.224
You don’t have to add anything to routing table: pppoe will add default route to internet and pfSense hosts will be accessible directly through bridge1-attached ethernet.
You will have to configure pfSense machines to use xxx.yyy.zzz.229 as default gateway (the network connection towards ISP1).
Since pfSense is doing FW, you don’t need to filter anything in forward chain. You do have to establish filters on input chain as RB will be fully exposed to internet.
Then you do similar for MT en route to ISP2. It will be more complicated if routable addresses really don’t belong to single /29 subnet.
[edit] In this case you can dedicate ethernet ports one per pfSense host without creating bridge on top of them. Then use /32 addresses for point-to-point connectivity as discussed in this topic.