Break all of your questions down to to subject and look for a forum on the right side of the main forum page that matches your question, then post your question.
What also helps for your question say on how big
should a swale be is to post pictures of the site you are wanting to put a swale at and tell why you want it there, soil conditions may also help.
Do this for each question and you can normally get great help here, as permies like to help other permies.