You don't have to give any casino employee your ID, ever. You can show it to them if they need to check your age, but they don't need to take it into the pit (at which point they probably will rate you and give you a player's card if you don't already have one). When you play as a refusal, just tell them you don't want a player's card. If they ask for ID, you can show it to them, but there's no reason for them to take it into their possession. These aren't cops, they're just employees of a casino.
I say you should spread like crazy because it will be the best way to maximize your profit. If you're playing nickels, a 1-16 spread might save you. If you're playing heavy green/black and spreading 1-16 with the count, you're eventually going to find yourself unwelcome anyway. It would be wise to spread more so that you can save money in low/neutral counts. Wonging out is also helpful. I've regularly spread between 1-40 and 1-60 at nickel games in the past with no heat during short sessions. On some of these games, my EV has been over $75/hr. The same doesn't necessarily apply to bigger games, but neither does the opposite advice to spread small. Just because the books say that 1-12 is safe doesn't mean it is; once the big money's on the felt, they'll watch you no matter what.
And yes, you'll raise more suspicion playing as a refusal if you're playing mid/high limits. If you insist on playing black only, you'll be playing in a lot of high-limit pits where you're automatically under scrutiny anyway. It seems to me like a better approach would be to play quarters, spread like a maniac ($25-2x$400 is alright, but hey, if you think your act is good...), and avoid HL pits. Play short, unrated session, and heat be damned. If/when they bust you, stay away from that shift for a couple of months, play at a different casino down the road, etc. They don't have your name, which is a big edge for you and is the key to this type of strategy.
As for avoiding backoffs, learn to notice the warning signs. The easy part is counting cards and making the right bets and plays. The hard part is pulling it off. Pay attention to what people are doing in the pit. Pay attention to body language. If the phone rings, try to eavesdrop or at least see where the person on the phone is directing their attention by way of inadvertent gaze. Pay attention to the mood of the boss/floor. Watch for backs purposefully turned to you. Notice the whereabouts of security, suits, or other personnel standing in the pit or, more alarmingly, behind your table. Sometimes there's nothing you can do, but sometimes you can see the axe coming if you're alert and paying attention. Hope that helps.