there is no SIM in this device
Enabling "Easy Wake Mode" does the trick, but isn't that detrimental to battery life (doesn't it create a wakelock?).
Easy Wake Mode does not create a wake lock, all it does* is disable the stock lock screen, and the stock lock screen is normally responsible for blocking the volume buttons from waking the device.
(* Okay if you have pin/password it does some tricks, but without security it simply disables it).
WidgetLocker only holds wake locks for a few seconds at a time, right around screen on or screen off just to give it some time to work.
Android behaves a bit funny when there's not a sim card in a device. It more aggressively wants to show the stock lock screen because that tells you there's no sim card. I've known about this conflict but it rarely effects actual users as they tend to be using phone with sim cards. I ended up putting dummy sim cards (no service) into my test phones to avoid it. I'll keep this in mind (and have one idea that might work), but for now I recommend either throwing a spare sim card in there or using easy wake mode. Airplane mode, and then reenabling wifi, might work also, however then every time you reboot you'll have to manually turn wifi back on.
Is it normal for WidgetLocker to request SuperUser every few minutes?
No. WidgetLocker requests it when first starting, if you have root helper enabled. There's also a special case on Samsung devices, due to buggy Samsung firmware corrupting app data and WL detecting this and using root to fix it, but it's a one time operation only (Unless you deny the request).
But if you're running a task killer, stop
This.