There are some brokers who can provide 1:500 leverage, so people who are interested in investing in forex can start up with a small capital.

The risk are more or less the same if you are going to start with a higher capital. If your start up capital reach certain boundry then the there will be lesser leverage given to u, i.e. If you have made a deposit of 100k USD, u can no longer trade with 0.01 lot, you have to trade with 10.00 lot.

There's nothing wrong with opening an account using 100 dollars. But will you want to slowly grow your account given that your return is roughly 10% monthly which is 10$ per month? Or trade with a 10,000 account and gain 1000$ per month?

That is entirely up to your interest in forex. For educational purpose or take a chance.

Also, the market is extremely volatile. Some broker only provides smaller pips for the currency pair (price movement of 0.00001) or larger pips (0.0001 price movement) but the catch is that the larger pips brokers often do not provide big leverage, which means your lot size have to increase for each trade, so ur account will burn out faster with ur 100$. So choose ur broker wisely and know what type of account they are providing.

If u r going to open an account, dont bother ur broker who keep asking u to deposit more $$. U must maintain ur status quo, or else u will burn ur $$ faster.

Have a good read.
http://www.investopedia.com/ask/answers/06...andpipvalue.asp

The broker does not reserve USD50 from your margin. They use it to open the position size you required. So a 0.1 lot of EUR/USD at current rate with leverage of 200 is USD55. So they take USD55 from your USD200 to open the minilot. That leaves you with around USD145 as margin.

So if you decide to open 0.2 lot, then it would cost you USD110 from your USD200 and that leaves you with USD90 margin. It all depends on the lot size that you open and how much margin you have left to play.

Your calculation on pip movement and margin call (when you run of margin if the market moves against you) is correct.

stop loss or take profit you set must differ from market price by at least X points

Your broker need you to set tp/sl 160 pips away from current price.

Nope... its not  normal... change broker pls. 

More disturbing when I saw your spread. 
You should change to ECN broker.