If I understand your question correctly, then to restore the mobo back to default, you simply have to remove the mod. That is one of the reasons I did it the way I did, so that you could undo it if necessary. However, be aware that soldering pin 97 and pin 102 back down is rather tricky because of the fine spacing of the pins. A fine tip soldering iron is definitely a must.
As far as testing the OTP, um, unless you have a CPU you are willing to sacrifice, I don't know of a way to test it. In my case, I actually took a chance with my CPU to try it out. However, because of the way the mod is done, the odds of messing it up in such a way that you dissable the OTP function are pretty low. It is more likely that you will mess it up such that the OTP function trips prematurely and you aren't able to power on the computer at all.
As for the northbridge, does it have a thermal diode? I didn't think it did. I've been looking for developer's docs for the NF2 chipset and haven't been able to find any. I'm guessing I need to sign an NDA with NVidia to get them.