Well, its all opinion based... so let me start with - do what comes naturally to you. To all writers, the writing style and methodology differs. There is no best practice - again, as per my opinion.
What I would do -
Ques 1 - don't let the ideas go away... write as much as you want and in any form that you want. You can write a hundred stories at a time if you want to. Don't limit or constraint yourself. Ofcourse, this will have its disadvantages too. You will be tiring yourself. Better, make plans (outlines) for your story plots. And whenever you get an idea reg any story, add it to the plan and then to the story. If you get an idea that doesn't fit anywhere else, write a blog about it or just list it in a random-ideas list so you don't loose it.
Ques 2 - I have the same issue. My parents have no idea I love to write or the amount I write. However, my friends know I am insane about such things... if I get an idea, it needs to be penned down immediately. My grandfather and friends have read my work... and then I blog about it. Luckily, I have friends I can discuss ideas with.
You can find many online forums where people share and discuss ideas. But be careful - the ideas online can get stolen and you may have no right over it once it becomes part of something big. I have been part of forums where people wrote serial fanfics and ideas were taken from there. We were happy to see our ideas materialize on our fav shows but could never let them know that we did the brain work behind those ideas.
Hope it helps :)