HMX production rate estimation:
HMX is the most important ingredient in NEPE-75 production and the HMX itself is almost exclusively used in solid propellant & dynamite. So it is a credible indicator on how many propellant CASC can get therefore how many ICBM they can produce upon them.
I have no concrete proof on accurate figure but here is some guess work based on official wechat news or bidding information.
China has only one confirmed HMX production facility, Gansu Yinguang Chemical Industry Group, a subsidiary of NORINCO.
The internal designation for HMX is Product 101, for confidentiality purpose and it is produced in their 4th chemical plant.
The project of "solving the bottleneck problem of 101 products filtration" has increased the production capacity by 50% and generated economic benefits of more than 30 million yuan.
HMX approximately costs 80,000 yuan/t according to a journal, meaning the annual production rate is close to 1125t/a. And the news was written in 2020 where two rounds of production expansion was completed in 2015 and 2018, exactly the same time PLARF reorganized with massive brigade expansion.