There' s no judgment here...my English is as terrible as my French!
I still don' t know whether the Original/Translated Port is for the source or destination, but it now sounds more, at least for the IPs, like you want to translate the source.
In this case, you could restrict the firewall policy to the one host as the source, and create an IP pool for the NATted outgoing source IP.
If the original and translated ports are the source, you could forego the IP pool and do both translations (port and IP) with the Central NAT Table.
If those two ports are the destination port which needs to be mapped, then you will need a combination of a VIP and an IP pool in the policy; the IP pool for SNAT, and the VIP for DNAT.
Leave the external IP and mapped IP the same (both the public destination), but map the port.
Regards,
Chris McMullan
Fortinet Ottawa