More information on PanAm's first trans-Pacific flight I have came across this answer, about PanAm's first trans-Pacific flight (SFO-MNL route via HNL, MDY, AWK and GUM). For the text, I'm working on, I was wondering, if there is any source that can provide more information on this route.

Literally:


years of operation,
approx. times needed to flight each segment,
approx. break times (refueling?) times at each mid-point,
was passengers allowed to leave the airplane during each break?


I'm also interested in getting answer to a question that might be harder to answer (too broad?). How it was possible to service / refuel airplane on airports marked as uninhabited in the original answer (MDY and AWK)?
There are many sources of information about these flights that you can find by doing an Internet search. For example, I just used "panam clipper flight sfo to mnl".  

The following links should get you started:

In addition to some aircraft information, this link has a schedule image about halfway down the page:
https://www.pacificaviationmuseum.org/pearl-harbor-blog/pan-ams-pacific-clippers/

This link has more Manila-specific info, with a video. 
http://www.lougopal.com/manila/?p=1463

The following link, in the paragraph "Building Bases Across the Pacific" will answer your last question regarding MDY/AWK:
http://www.clipperflyingboats.com/transpacific-airline-service