How can I solve this BootCamp partition mess I've created?
Boot to Internet Recovery Mode
Open Terminal in the menubar > Utilities
Enter diskutil list to get the disk identifiers of your internal SSD (probably disk0), HDD (probably disk1) and the CoreStorage volume (probably disk3 or disk4 - apply the disk identifiers below according to the findings in your environment)
Now remove the seven partitions on the HDD with gpt:

diskutil umountDisk disk3 #the device identifier of the CoreStorage volume
diskutil umountDisk disk1 #the device identifier of the HDD
diskutil umountDisk disk0 #the device identifier of the SSD
gpt remove -i 9 disk1 #the device identifier of the HDD


Repeat the above steps six times but lower the index number (-i) by one in each step:

diskutil umountDisk disk3 #the device identifier of the CoreStorage volume
diskutil umountDisk disk1 #the device identifier of the HDD
diskutil umountDisk disk0 #the device identifier of the SSD
gpt remove -i 8 disk1 #the device identifier of the HDD


...

diskutil umountDisk disk3 #the device identifier of the CoreStorage volume
diskutil umountDisk disk1 #the device identifier of the HDD
diskutil umountDisk disk0 #the device identifier of the SSD
gpt remove -i 3 disk1 #the device identifier of the HDD

Resize the CoreStorage stack:

diskutil cs resizeStack lvUUID 2120g


with lvUUID: the UUID of your Logical Volume (8DC64131-3881-4971-B870-2FB6BFB58EDB)
Reboot to your main volume
Reinstall your current system to recreate your missing RecoveryHD or use this tool Recovery Partition Creator




Instead it should also be possible to merge all partitions (disk1s3-disk1s9) to free space and expand the CS LV then without booting to Internet Recovery Mode (untested):

diskutil mergePartitions Free Space disk1s3 disk1s9


Then reinstall your current system to recreate your missing RecoveryHD or use this tool Recovery Partition Creator