You just confirmed my theory ( acctualy not theory but anyway ) by visiting ford dealer for FDRS conection for IPATS, Im more than sure they cary out ECU SW replace as well to match your engine specyfic. Actualy it is possible also if you have ETIS account and from there you can buy access to ford server for different prices, cheapest is 8 euro for 15 Minute access I believe... not sure .
Anyway , im happy You carry out this problem, and can enjoy your car again
It's not even close to IMMO OFF - It;s IMMO emulator. So every time You change your ECU , You must carry out work , by removing memory chip, reading it out , coppy immo code from it , and place it in that emulator.How does the immo off work then? Something like this https://www.youtube.com/watch?v=P1C97Y8b70c
In my opinion way expensive, and time consuming way than 8 euro in ETIS, with less than 2-3 min time .In the end You keep your hands clean ...