DaMadFiddler,
One thing I've always had to do after making a set of System 6/7 floppies is "bless" the System Folder. To do that, you go into the Disk Tools floppy, open up the System Folder and then close it again. This "blesses" the System Folder so it will boot.
Another tip, if you have access to it, is to get a Mac model that is currently booting 6 or 7 and use that to create sets of System disks. If not, then you can try and pull it off with a Mac emulator like Mini vMac or the like. For example, I own a Power Mac 7500 and it boots into OS 9.1. But I use it to make boot floppies all the time, since it is at the level closest to understanding and dealing with Classic OS resources.
As for both SE/30 logic boards, at this stage I would recommend replacing all of C1 through C13 capacitors using Trag's recap kit, since cleaning didn't fix the problem and swapping SIMMs didn't help, either. If you's like me to do the recapping, send me a PM (private message) and we'll go from there.
73s de Phreakout. :rambo: