You're not "reprogramming" a Nissan ECU from 1997.
Sounds like you have a lot of planning to do. A DOHC KA will handle low boost with a standalone, but to make any meaningful power, you're doing a full rebuild.
An SAFC is a cheap shortcut, from decades past. Proper tuning requires more than simply modifying the MAF signal. I've been down that road several times.
Your fan is the least of your concerns - a properly-functioning stock clutch fan and cooling system is more than capable of handling heat (even here in AZ).