yes, it is safe and most people in this forum will agree that it is safe as long as you are cautious and of course it is worth it.

there are a lot of lists of gambling sites with high reputation that offers great games, events, giveaways, tournaments etc..(every gambling site differs) including the gambling site I advertise Stake.com

It depends on the situation, you can only call it "make a living" if you are earning from it.