In gold, 1 hand is 100 ounces, and you can earn $853. 0.5 hand is half.
The second question, you didn't provide how much margin you have. Let me give you an example based on your 1 question.
For example, if you fall to 129 1.67 and 0.5 lots, and you lose $426.5, then you must have at least this amount of available margin, and the total margin should be added to the margin required for buying gold.