We don't have any statistics on whether members of the ELU community are native speakers or not, and that's deliberate. There have been a number of Meta questions asking whether that sort of identification would be useful, but they have always been voted down.
The reason is that, while there are a large number of native speakers here, not everyone is; and the skill in explaining why something is done is generally exhibited by those who have had to learn it rather than those who have gained the knowledge by immersion and osmosis.
There are also native speakers who have actually formally learned it as well as picked it up natively, of course (we have at least one professor in English on the books, and quite a number of people who have studied English to degree level and beyond); as well as those who can explain without having the formal learning.
There are also people who post incorrect and unsubstantiated information, and they could be native speakers too.
In short, nativeness is no particular guarantee of quality or correctness.
The question limit was introduced in 2014 to help new users learn the ropes on the site and provide good questions. It also means that you do not wear the community out with lots of questions — this can reduce the quality of answers and influence voting. There are a number of Meta questions from the time about it.
50 question per month limit? (27 February 2014)
Follow up to FF's question on 50 posts limit (3 March 2014)
Do we want to enable post limits? (24 July 2014)
Note that not only is there a limit of six questions per day, but also a limit of fifty questions per month. I did some analysis in an answer on the July question to show the effect on one prolific poster.
Do have a look at a question on research requirements. Six good questions per day would indeed be prolific.
If you're learning English, you may be interested in our sister site for English Language Learners.