1. Yes, this is possible. When leverage is set to 1, it switches to a no leverage mode and margin is not accumulated anymore. I don't know the reason of this - maybe this was implemented for a special case of direct market access. I'll look into this, we'll probably remove that special case for the next release.

As to my knowlesge, IB are a leverage broker and have no fixed margin cost.

The Z8 lookback period simply depends on historical data of thee default assets. You can not backtest assets that didn't exist at that time.