I think your situation is salvageable, but I'm about to meet some people for dinner. We just need you to be clear about things because it has been a little confusing.
If you can switch to your unsafe system then things can be fixed.
I guess I misread the situation if you are able to get your system to boot at all. So you tried to fastboot back to ICS and that failed for obvious reasons, but you can still access safestrap?
Try flashing this to your stock system:
D4 stock De-Odexed JB 98.72.18
It's a stock JB OTA rom, just deodexed. If you've already applied the update, this should be compatible with the jb kernel.
Additionally, and someone please correct me if I'm wrong, if you're able to boot into that rom, try uninstalling safestrap and applying the official update. Updates are able to be applied on top of themselves. Assuming that the fact that the rom is deodexed doesn't make you fail the update, you should have things about cleared up.
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Before you keep flashing stuff which may screw things up even more, we need to know exactly what you've done.
Did you apply the JB update?
Did you try to sbf ICS? If so, was that after applying the JB update?
Are you still on ICS and tried SBF and it failed?
I tried to SBF ICS, which was after applying the JB update.
As far as I know, the kernal is on JB, but after I accidentally restored an ICS backup; I am not exactly sure what it tries to boot into at this point.