Much depends on your risk tolerance, asset class, volty, etc... It's not unusual to have 10% weeks in exotic options.
He's telling you that to be a profitable trader, you must first focus on and manage your losses. Every profitable trader learns to manage their losses first, and then they can develop a method (plenty on this website for free) of placing winning trades. With an account the size of $40,000, if you limited your loss to $800 per trade, that would be 2% of your total capital base. You are asking the wrong question. The correct question for any trade you place is: How much can you lose?
No, $400 is not high IMO. I trade with 26-27k account. (I take out the profit each week.) I've been averaging about $420 for the last 2 months. (I've been daytrading for only about 5 months ) Good luck.
depends on what kind of leverage you can get on that 40k, which if you go prop can be a lot. 400 a day is about 100k, there are a lot of people on elite making more than that a year. so my answer to your question is, yes and more.