Report on Broker's profitability on Algorithmic trading in general or on FX margin accounts?

[HobbyTrading]

If you are a professional profitable trader, how do you manage the margin while mixing trade #1-Manual and #3 -API-based_Automated-Strategy?

Both manual and automated are done on the same account. So there is no need to separate margin usage calculations. Just make sure that the sum of both is below the maximum which can be handled with the account size.

And what about your broker's compliance as to how they see your trades?

The broker's compliance is the broker's responsibility. I don't worry about that.

e.g. you made 100K manual trading and you made 100K by automated strategy EA/Robot that you run on a server on the US-based server, how this annual tx will be calculated?

I don't use a server based in the US. My second computer, at home, is my server. You are making too many assumptions about what others are doing.