MySQL QPS debugging?
As SQL, show global status like 'com_%' will show you a break down of the types of queries. Any high volume of update, replace, delete should be an indication that you shouldn't be using MyISAM.
Given there are 5kqps SHOW FULL PROCESSLIST at any instant should give you a sample of activity.
Don't worry about IOPs, focus on the queries and watch the benefits flow from that. If queries are contained to the primary key there is no reason for them to result in disk IOPs. Filesystem cache is also used so that's another buffer preventing IOPs.
If its the IOPs (hardware not handling it) that's the problem consider moving to InnoDB. If you value your data, move to InnoDB.