Wow… This is very thorough analysis! I see a huge effort behind this work 
Nice intro, questions asked, data preprocessed and munged to find out the answers.
Job very well done!
Speaking on conclusions, I think there is a topic for research. Probably, DETE employees see more opportunities for improvement, rather than showing dissatisfaction? Otherwise why would they stay there for so long? In other words, I was puzzled by level of what is called “dissatisfaction” in this research growing together with age? Or was that number of years worked at DETE? Experience level is a bit confusing here.
Also, if I may suggest, I would separate data processing part and research part. Those interested in code are distracted by graphs, and those interested by research itself loosing the line between pieces of code
Probably, part one could be like these are the questions, let crunch some data this and that way, here are the results. And for institutes it would be rather easier to understand the pure story without the code. Like, we have processed data from such-n-such amount of people, these were the questions and here are our findings.
Overall this is very-very solid work. Congrats on a job well done!