Because I have more memory to work with in the N800, I'll just have to extend the current in-memory image to extend to a square the width of at least the diagonal of the fullscreen display plus one tile, which equates to a 5x5 tile square (1280x1280). Then I'll use standard GDK image processing to rotate and center that image as necessary, optionally using smoothing to keep it readable. It'll probably require at least 4 times as much memory (twice the number of pixels in memory, plus an intermediate buffer for the rotation processing), plus a lot more CPU requirements, but people have been asking for rotation for a while, and with the N800, it's a lot easier to digest.

This might be nice for a third-party application (even if it's written by me) to consider doing. I don't think it belongs in Maemo Mapper proper.
I think that's up to Nokia. I have done everything I can to debug this, but the seg fault is in GLIB code, which (to me) implies an improper handling of the "out-of-range" or "device-turned-off" event. Note that this bug is not present on the 770 (even though Maemo Mapper's code is identical).
That is already in progress. For what it's worth, the very first version of Maemo Mapper was less than 1,000 lines long, and I kept it in a single file to ease development and to improve performance (it's easier for the compiler to optimize code in a single object file). Obviously, the project has grown considerably since then.

Thanks for the feedback.