I have been searching, but this specific solution I have not found. I am sure some users more experienced with MikroTik facing the ISP equipment could help.

Setup:
My client has Bahamas TeleCom (BTC) Fiber service coming in and terminated at a ME 3400 device.
The Port1 from the ME 3400 is connected to Eth1 on my Mikrotik
The information they sent me was as follows: (leading IP address numbers are fictitious)
999.000.235.137/30 - Port1 on ME 3400 device (BTC provided)
999.000.235.138/30 - Eth1 on Mikrotik (what BTC says we are supposed to assign on our device port)

Then BTC gives a "Route Statement": "IP route 0.0.0.0 0.0.0.0 999.000.235.137" (I think this just means they want the "default route" to be to .137)

Then BTC provides more: (please note the 555.444 fictitious range is actually a public IP range they are giving - not a local range)
Network Subnet: 555.444.34.152/30
LAN Interface gateway 555.444.34.153/30
Usable IP: 555.444.34.154/30

Typically I deal with the ISP providing the final Public IP address, Gateway and subnet information, but, in this case, the client decided NOT to "rent" the BTC Fortinet router. Now I am wondering if I can do the work of the Forinet on the Mikrotik and eliminate the need for a router between the ME 3400 and the Mikrotik.

I have read suggestions to do a 1:1 NAT translation from the 555.444.34.153 to the 999.000.235.137

If the 999.000.235.137 is coming in on Eth1 in the Mikrotik, do I setup the 555.444.34.153 on a bridge interface, or can I have BOTH addresses assigned to the Eth1?
Then do I do srcnat and dstnat rules, or I have seen some suggestions on netmap?

Thank you in advance for any help. I am having to do all of this remotely connected to a laptop with just an LTE connection, so I am not in a great environment!

-Keith