Free margin confusion

Dear members,

Does anyone know how free margin actually work,
Suppose i have 100 dollars, open position with 50 dollars,
now my free margin is 50 dollar and equity is 100, as equity goes down free margin also do same
I want this 50 dollar position to move in full jurisdiction ( with 100 leverage. stop loss and take profit 100 pips down and up)
position go against me now my equity is 80 dollars and free margin is 30.

  1. Can i open another 50 dollar position as my free margin is 30,
  2. if not this mean for position of 50 dollar , broker froze another 50 dollar from my account. :mad:
  3. if i open position with full amount of my account, free margin is zero now, will he go in negative when position go against me.

Thanks in advance for replying.