I did that, nearly a year ago, and can throw in a thought or two, but with no promises that they'll help.
You're slightly closer to being a scalper than I am, I'm guessing, from your general description - even though your description of letting things run doesn't really fit my picture of scalping at all.
I would still suggest that you at least consider the possibility of using constant-volume charts rather than tick charts, for futures. The reason I switched from Forex to futures was that on the advice of ex-institutional trader friends who were very familiar with how I trade, I wanted to be able to use constant-volume bars. I just wish I'd done it earlier (and am saying that as someone who made what most people would call a decent living from spot forex for quite a while before switching).
I spent 6 months looking at ES, CL and NQ (planning to switch, while I was still trading forex), and decided to go for NQ as my primary instrument, rather then ES.
The advantages of ES are all the ones you already know about (and probably the reasons you've selected it). I offer the observation that for someone used to trading EUR/USD and Cable, as I was, NQ is overall much more like what you're used to looking at. I'm glad I chose it. Yes, ES does have bigger volume (of course) and probably, overall, better fills (just about), but it's as boring as hell and will try your patience, if you're used to scalping forex. Just my perspective.
I use IB and like it, but won't advise about brokerages. I haven't compared enough to have any insight to offer.
It's however fast you set it to. You choose the number of ticks just like you'd choose a temporal periodocity if not using tick or constant-volume charts. I strongly prefer constant-volume, myself.
This comment confused me and I don't really know how to respond to it, except to state the obvious, i.e. that you get to choose what speed/tick-count/volume-count of charts you want to trade from. If you're talking about, for example, "the amount of action there is in an n-minute period", I was coming from EUR/USD and preferred NQ because ES felt like watching paint dry and I wanted something that moves a bit more. Just my perspective (but I'm guessing from the wording of your questions that it might be a rather different one from yours, in which case just ignore me on this point!).
I feel a bit cheeky "endorsing" WRBtrader's comments, given that he has far more experience than I, but this is clearly right, and pretty important.