Good questions and thanks for asking. I did some investigating. Unfortunately it turns out the Omnimount bracket is not heavy enough for the LX arm's pivot --the arm itself adjusts fine but its pivot wants to turn upward (apologies for not getting that info sooner). In our current product offering, the Neo-Flex LCD Arm (45-174-300) might be worth considering--it has no minimum capacity requirement and features a full tilt range. Regarding whether the bracket will hold an iPad when tilted down, yes, it will if its spans are well tightened in place. But there isn't much margin for error: if one of the spans moves a bit or they aren't tightened quite enough, the tablet could fall out. An iPad case with a stickier exterior could help, but in your application where you want to keep the tablet tilted down a lot, you might want to consider this iPad bracket instead: http://tabletwallport.com/iPad_Wall_Port.html
(don't know if you'll have an easier time finding it in DE).
Regarding the YouTube vid, the arm shown is the older style, but before I comment more on this subject, it must be repeated: modifications like this could void your warranty. You could still perform the modification and increase the downward tilt by roughly another 25 degrees on your newer-model arm. If the tabs were completely removed, you'd get still more tilt. Again, I'm not recommending you do this.
Let me know if you have more questions.
UPDATE... Ergotron now offers an iPad adapter: viewtopic.php?f=7&t=45&start=10