Your scenario is burdened by excessive detail about FAI. Any situation in which people create lots of sims but don't allow lots of suffering/horror in the sims (perhaps as "rescue sims," perhaps because of something like animal welfare laws, or many other possibilities) poses almost the same questions.
I thought about the "burdensome details" objection some more and realized that I don't understand it. Do you think the rescue sim idea would work? If yes, the FAI should either use it to rescue us, or find another course of action that's even better - but either way we'd be saved from harm, no? If the FAI sees a child on a train track, believing that the FAI will somehow rescue it isn't "burdensome detail"! So you should either believe that you'll be rescued, or believe that rescue sims and other similar scenarios don't work, or believe that we won't create FAI.
This is our monthly thread for collecting arbitrarily contrived scenarios in which somebody gets tortured for 3^^^^^3 years, or an infinite number of people experience an infinite amount of sorrow, or a baby gets eaten by a shark, etc. and which might be handy to link to in one of our discussions. As everyone knows, this is the most rational and non-obnoxious way to think about incentives and disincentives.