Sorry to hear that. A couple of ideas, though:
-Maybe your CD300 isn't totally dead... since the problem arose when you tried to eject the CD, those noises and smell could come from the tray's motor, but everything else could be fine. My CD300e does rattle upon powering up, ejecting and inserting a disk, but works great otherwise. You can try to open it manually with the straightened paper clip and insert a CD manually all the way, and see how it reacts -- try with the device disconnected from the computer first.
-SCSI voodoo is likely to be the cause of your other problems -- removing a device from the chain can make it go crazy. Try to revert to the same setup and cabling -- including the suspect CD300 turned off. If that works, it's just a matter of finding the proper termination/device order/cabling. Not that unusual.
Hope this helps,
2xSE/30, Colour Classic, Mac II, IIx, 3xIIsi, LC, LC475, LC575, Power Quadra 700, Quadra 840AV, 2x5200, 7200/90, 7500/132, 7500/233, 7600 G3/450, PowerBook G3 Bronze, iMac DV SE, MacMini G4, MacMini Core2Duo, iMac 21.5" i5... and SGI Indy R5K