Measure the voltage at each test point on the rectifier board. 6 flashes I believe means it isn’t getting 43V. You will need to have one probe of the multimeter connected to ground and the other on the test point. The manual has what the voltages should be. Compare and report back.

Actually, before you do that, with the machine OFF, check continuity with your multimeter between the ground wire at various points and the coils and other high voltage contacts. That may indicate whether you accidentally created a short to ground anywhere.

https://toolsweek.com/how-to-check-continuity-with-a-multimeter/

If your coils are getting continuity to ground you have a short, and that isn't right.

F4 is your solenoid voltage fuse. You are assuming it's because of the playfield swap that the fuse is blowing but very well could be something else. Replace the fuse, disconnect connector J1 and J3 from the rectifier board and check TP5, you should get around 43v. If your voltage is good, reconnect J1 and J3, and unplug all the plugs from the solenoid driver board except for J3, see if the game will boot. If the fuse blows then you have a problem on your solenoid driver board.

So with that you've determined your rectifier board is good, and your solenoid driver board is good. Next step would probably be to disconnect all solenoids on the playfield, then reconnect them one by one until you find which one blows the fuse. It's a PITA but if you don't see anything wrong you have to narrow the problem down somehow. Also, you said playfield lights are locking on. If you mean the controlled lights like under the inserts then that's not good. Likely a short somewhere with the braid causing them to get locked on.

Wires swapped on one (or more) solenoids would cause this too, right? Might be able to visually inspect that all the right wires are on the correct side of the diode on solenoids.

You probably have the 43v bus wire wired incorrectly or shorted to something. You can try pulling the playfield fuse and if the fuse does not blow then trace out the 30, (yellow) solenoid bus line and make sure it only goes where it is supposed to. It should daisy chain to all the playfield coils, soldered to the band side of the coil diodes.