I don't think TalkBack mode alone is the culprit here, but you must have enabled "Explore by Touch" also when you activated TalkBack, which makes things tricky.
If you just have the regular swipe to unlock feature for your lock screen, to unlock it, you'll need to...
Use TWO fingers and swipe the screen, but make sure your two fingers are separated, because if they are too close together, it'll think you're using one.
That's it. That should unlock the lock screen. You don't have to worry about tapping on anything like it says; that is only if "Explore by Touch" is not activated (just TalkBack).
Now, to disable TalkBack mode, you need to make your way to "Accessibility" in the "Settings" and toggle TalkBack off. On my Galaxy S3, I can just hit the Menu hard button and double-tap on Settings, but I don't think the Tabs have a hard Menu button, so just head to the Settings as you normally would using two-finger swiping, long pressing to select, and double-tapping for enter.
For instance, to access Settings from the Notification tray...
- Make sure to use TWO fingers (slightly separated as before) and swipe down from the top to open the Notification tray.
- Then, touch the "Settings" symbol once, then double-tap it to open it up.
- Use two fingers to scroll down to "Accessibility" and press it once, then double-tap to open.
- Then, press once on "TalkBack" and double-tap it.
- And once on the "On/Off" switch, and double-tap.
- Then do the same for "OK" and you should be good to go.
Quite a pain, I know.