Again, I have linked to how much USSR have spent during 1980s. It is 13% of GDP. I never argued that is the number PRC should follow.
I respectfully disagree about your statement saying that spending between 4 and 5% of GDP on defence is "unhealthy". The country I live in right now, which is a NATO-member is often known for its "peaceful reputation" worldwide (albeit a very false reputation, I would say) and Trump has managed to scare the current government here to spend just under 4% of its GDP on defence.
While I do not like the defence spending here, I can assure you that we won't collapse because of those 4% spent on defence. That, you can be very sure about.
DPRK is sanctioned with most brutal sanctions, but the situation is still better than being Somalia, Mali, Chechnya, Moldova, Ukraine, Iraq, Syria, Yemen, Sudan, etc.
There is no "national development" if the country is dead and simply does not exist anymore.
Either way, I won't discuss this topic here. Let's rather see how Iran is about to get bombed for the third time since last year and how much they can hold out.