There is no maximum amount limit. Some payment methods have daily deposit limits, such as bank card deposits. Check information for the payment method first. Skrill has no such limits.
I am curious, is profiforex still taking U.S traders? I have searched on the website for this information, but nothing. I read somewhere that they stopped accepting U.S
U.S traders are still accepted. There has never been a time when the broker placed a regional restriction. You should check the country list on the registration page.
I ran into a negative balance in one of my micro accounts and the broker agreed go reset it to Zero. I thought I would be asked to pay the negative. So, it is actually true that Profiforex provides negative balance protection. This is really good.
There is no restriction to how much you can have on your account. However, when choosing a deposit method, you should find out what is their maximum amount per transaction. I think there is no maximum with Skrill, Webmoney and some others.