If you get any serial output from MorphOS, then it means that serial debug is indeed active, which it sounds like it is in your case.

If you then don't get any serial output at the time something crashes or hangs, then it means that it at least didn't crash in any normal way caught by MorphOS.

Due to the varied crashes and errors you get, it really sounds like there's something going on with your system that's maybe caused by a hardware problem somewhere.

Please remind me what your setup is like: What PCI/PCI Express cards do you have installed, and which storage devices are connected where? Which storage device(s) are in use when you try to install the SDK?

Also on my own Sam460, it tends to get rather unstable in general when it overheats, which it in my case does by default. I have a 120mm fan pointed at the CPU. With the fan, the system functions normally. Without the fan, the system often hangs especially when doing I/O to my hard disk. Is there any chance you can create some additional air flow in your system to make sure this isn't happening to you too?