I’ve made a “Adobe Cache” folder on a different drive and redirected all caching there. It’s easier to empty and it’s also easier to follow the size of the cache.
The pixel aspect ratio has nothing to do with your comps aspect ratio. If you have 1920×1080 square pixel footage then your pixel aspect ratio in Mocha should be 1.
They probably want a DCP package. I’ve used this: https://opendcp.org/ and you can get a JPEG 2000 codec here https://www.fnordware.com/j2k/ If you want to render it yourself. You need to stay in the Digital Cinema specifications or else it won’t work in th DCP player.