There are several issues here.
300GB/week is a large ingestion rate. Do you have any problems with keeping up? If you do, we can discuss that.
Yes, you could spread ibdata1 across the drives like you show. However, you have to do that before you start, or else play some tricks with the allocation. Which is your case?
Have you tested the DELETEs? I strongly suggest using PARTITIONing, and partition BY RANGE with daily partitions. DROP PARTITION is _much_ faster than DELETE. Yes, the space will be recovered. However, if you ever accidentally bump up against the limit (of disk space), it could be hard to recover from.
See this for discussion of PARTITIONing:
http://mysql.rjweb.org/doc.php/partitionmaint
The discussion is very close to what you need.
innodb_file_per_table -- If it is 0, all stuff will go into ibdata1, and your innodb_data_file_path is relevant. If it is =1, you will have trouble spreading the file across the drives.
If you could RAID-stripe the drives, much of this discussion goes away, and performance will be better.
Purging will _not_ un-autoextend. ibdata1 never shrinks.
So,... Answer my questions above, then we can focus better.