You are certainly living up to your name. Was Dumbass already taken? Slippage for limit orders? I would guess you would have to say it's infinite if you don't get filled. Market order slippage? Don't know about ES, I leave that to the SCT geniuses, but I see the NQ spreads go to three ticks like it was after RMH. And, ooooh, sometimes the fill takes a looong time. Odd, huh, what with several thousand orders being transacted per minute? Guess they just can't keep up.
Eh, limit orders are for pikers. Why try and guess where the market is going, let it tell you when to get in and out. Mkt orders or bust baby!
ES is almost always a 1 tick spread. During US trading hours anyway. Even during major announcements. This market can move VERY fast, but the bid/offer spread stays at one tick. There is just way too much liquidity for it to be any different.