Risk & Reward Tool Commissions

I have an issue with calculating communication.

My commssion is 2.5 per lot per transaction and raw spread for a EURUSD
It shows by default in the tool that commssion is 35.

1- what number should I put in there
2- If I want to risk a fixed dollar amount, let us say I risk 500$, is there a way ?

Regarding your last question, yes, you can do this, read the user guide here.