Stuck in DFU loop following downgrade

I know this subject has been generally covered before but I'm hoping someone might have insight into my specific situation. This started with an iPad1 (WiFi only) running 4.3.5. I wanted to downgrade to 4.3.3 for the untethered JB so I gave it a shot following various howtos (I did not have the SHSH from 4.3.3, I was able to get it restored using TinyUmbrella's TSS server). After monkeying around a bit too much I got myself stuck on a black screen and couldn't seem to fix it. Reluctantly, I let iTunes give it a shot and it successfully upgraded to iOS5 and all went back to normal. This time at least, I saved the SHSH, not that 5.0 SHSH will help much at this point.

Using what I'd learned so far, I gave the downgrade another shot. This time is was much smoother and I successfully restored to a custom 4.3.3 IPSW.

And here is where I get stuck. The iPad functions fine, Cydia and all, but I'm basically stuck with a tethered JB. I can boot it tethered with redsn0w but if I try to reboot naturally, it drops right into DFU mode.

So the basic questions are:

Is there any way out of this reboot-to-DFU loop?
Am I screwed because I don't have my SHSH for 4.3.3?
Even when tether-booted into 4.3.3, TinyUmbrella is only able to save a SHSH for "iPad 5.0gm". This seems relevant, is that my base problem?

Thanks in advance.