You asked for the one rule to drill in a simulator, so here is mine, and it is
duller than the mechanics you are studying: the stop goes in as part of the
same action as the entry. Not after the fill, not once you see how it opens,
not when you get back to your desk.
I say it that way because of how I found out. Before this site existed I ran
bots that traded other people's signals automatically with my own money. One
of those accounts did 24,641 closed trades and won 88.1% of them, and still
finished down $2,866, with 60 positions closed by the exchange as liquidations
along the way. Some of those liquidations were not the fault of the calls at
all. The bot was told to place a stop, failed to place it, and left a position
sitting there with nothing underneath it. On paper the strategy had defined
risk. In the account, on those trades, the risk was whatever the market felt
like doing.
That is the gap I would drill against, because it is the one the mechanics do
not warn you about. Contract size, tick value and maintenance margin are all
knowable and none of them ever hurt me. What hurt me was the distance between
the plan and the orders that were actually resting on the exchange. "Defined
risk" is not a property of futures, it is a property of an order that exists.
Two smaller things from the same period. Your instinct about the low intraday
margin is right and it is worse than you think — the number tells you what you
may open, and says nothing about what you can survive. And a simulator will
teach you sizing and mechanics honestly, but it cannot teach you the feeling of
a real position going against you, which is the variable that actually breaks
people. Nothing does, until it does. So drill the mechanical habit now, while
it is free, and go in small when it stops being free.