I'll try to find some other 8" floppies to the ABC800 this weekend, I also have another drive to test with. I don't have any 8" alignment disks.
I read them as MFM with 256 bytes sectors, and then I deinterleaved them with a block size of 4096 and concatenated the slices. Then I wrote a simple program that could extract the files. Apparently the filesystems varied a bit between versions, but it's a start. It doesn't handle continuation blocks and it doesn't parse the initial metadata block, but if anyone can come up with more documentation, I can easily add that.