切换身份的问题

I am holding 工作签证 and am losing my job. My I-94 expires at the end of 2013.  People recommend my applying for B visa to keep my status. I have a few questions：

 1). If B is approved and I get my job later, is it bothersome to get H-visa again? How long does it usually take?

 2).  After I-539 form is submitted to immigration bureau, is our status legal automatically？
 3）Should my kid (a dependent) apply for B visa? Is it better for him to apply for F-1? Or we don't need to do anything with him？

Thanks.