No,... Worst case scenario is that you change out all your harnesses and computer and your car still won't start.
But yea,.. Checking/replacing your harnesses and ECU seems like a good place to start.
Start with those two fuses and main relay. They're quite easy to inspect.
I would start by downloading the full service manual and wiring diagram for your car so you can print it all out and have it available there in the car with you (and save you waiting on pcb to upload the pictures)
then start testing continuity of wires. you probably have one (or several) wires that are broken internally like the fuel pump wire was. If it were me, since you KNOW the FP wire was broken, and know the color i would start to split-half method using that wire. find where that wire broke. Chances are if there was a rodent, fire, etc. any other broken wires will be in the same location. Could have been a spot the harness got smashed when they replaced the motor. could be a rat/squirrel/etc. got in there (they love to eat wires). Could be that something dead shorted and melted, which will generally melt any other wires in a close area to that failure point as well and basically short them all together in a mess of melted wire insulation with random strains of brown copper inside it.
If you can find this spot, you can repair the harness if you're decent at soldering (which i agree 1000000% w/pcb most people suck at it). repairing it would be significantly easier than replacing the engine harness.
having said that, i would still say don't get too deep into this thing and start dumping a bunch of money into it. not to try and judge you, but autoshop class in high school is nothing like diagnosing a car in the real world. by reading some of your posts earlier it doesn't appear to me that you've really got a good grasp of the auto electrical diag experience necessary to bring this car back to life. not to say with enough time you won't get it going (i hope you do) but i would really try to avoid dumping much (if any) money into this thing unless you have 100% condemned a part. That's the problem with even most "professional" mechanics now days. there really is very little "diag" in their mental toolbox. everywhere you go you have parts changers and that's about it. sure it takes less skill, knowledge, and expertise to just start replacing parts (eventually you will fix it this way, sure) but that's a VERY expensive way to fix a car. I'm the type to condemn the actual failure point of a part and replace that part. so you would first need to 100% confirm the harness in your car is good. If not, (which i would suspect) then find where it failed. if it is repairable (and usually is) then repair it. if not, then replace it. And even after that point, there's still a pretty good chance that the harness failure could very easily have smoked the ECU and/or other related sensors and the car still won't start. Reverse voltage or random catastrophic shorts ( like a smashed harness or fire) can do an awful lot of damage to sensitive engine components and sensors. you could very easily find yourself replacing one part after the other and believe me, it adds up. We had a brand new truck that got hit by lightning once... all said and done it was almost $20k worth of computers and harnesses before it was fixed. but once one part was condemned and replaced, it just led further down the troubleshooting tree to the next one... one giant snowball effect.