offset  length  value      description
0x1000   2      0x1010   absolute offset to block data
0x1002   2      0x15f5   which is constant along the whole file, I think, it is a kind of delimiter
0x1004   2      0x182c   ??????
0x1006   2      0x15f5   again the delimiter
0x1008   2      0x3208   relative offset to the checksum (relative to the start of this header = relative to 0x1000)
0x100a   2      0x203a   relative offset to object records
0x100c   2      0x283a   relative offset to track data. Every track data have the same header length = 44 bytes

this sequence of bytes is a special header also used in 3d object definitions. The very first integer means the absolute start of the data block. In this case it is 0x1010 which points to the very first byte of 3d objects table. The 0x15f5 is a bit strange since it is constant delimiter over the whole file BUT it differs among different files. Phoenix has 0x15f5 but Interlagos has 0x1a17.
On address 0x1008 there is relative offset to the checksum. It is relative to 0x1000. All relative offsets are relative to the start of the header.
On address 0x100a there is relative offset to object records table. There are 16byte definitions of different objects. I have discovered part of the format, it is described here .
On address 0x100c there is relative offset to track data. Each track has a 44 byte header in front of the very first track command (I hope it is 0xac). I haven't looked at this header, but it seems to have constant length of 44 bytes.