North Korea has had too much success, and too little failure to have developed this all on his own, so I agree with your take on it.
Folks forget that as Korea moves along here, it is undoubtedly transferring data to Iran, to help it in it’s process.
I recall a shipment of missiles headed to Iran from North Korea, that was stopped and sent back. North Korea sees Iran as a friendly state it wants to deal with, to coordinate with.
Don’t you find it odd that North Korea has not threatened the U.S. bases in Okinawa, Japan? The Marines 3rd Division is based there. The Air Force has a large air base. Why would they reach out to Guam?
Thus, Guam and and U.S. may be a distraction from the real target Japan. Who would want that.... China.
Here are North Korea’s possible moves or all the above.
1) EMP attack over Japan or the United States
2) Nuclear Attack on Tokyo, Guam and possibly U.S. bases in Okinawa.
3) Rocket attack on Seoul and 2 million man invasion of Seoul via the tunnels.