I think the magnets are the same across the fantastic four and other Williams of the time. JL don't pulse, they are variable timing, based on holding the button. BK is timed by the MPU and is adjustable, it is the only one of the four that act this way.

Are you sure you need the magnets? There is a relay involved too, have you test their outputs?

RX, man you spent a lot of money on a 'free' pinball machine. Happens all the time . That's a pretty good looking playfield.

You may want to start a separate thread asking for System 7 and/or pinballpcb help, you will get a larger audience. One expert on sys 7 is @schwaggs. He's rebuilt several BKs along the way.

I don't know much about those boards, but whenever you get new boards for an unknown machine you run the risk of shorting something out due to problems on the PF. The boards were taken out for a reason, and they may not have taken the time to figure out the root cause of the issue.

F2 blowing on startup is likely a shorted solenoid somewhere. You'll need to hunt that down. Check all the coils and all the tabs to make sure there isn't something dangling on one and shorting the system. Its a good idea to visually inspect the entire pf underneath to make sure nothing else is wrong. I've had loose GI wires and ground braids cause havoc with coils and switches.

I fear whatever popped that fuse popped your IC1 again. You'll probably need a new one. When you get it, disconnect all the PF connectors and display from the MPU & driver boards. A working board set will boot and clear the codes without the PF.

Inspect the Display board and connections then connect it, make sure it boots and you have displays. You should be able to connect the coin door connector without much risk if you want to do resets with the buttons.

Then pray and hook up your playfield, do it in steps so you can identify issues if they are still there. Do your lights, then your switches, then your solenoids etc.