I think for the 08+ ones the screws should be fine as it bolts in from the back whereas mine bolted in from the front(07) I did have to get longer screws to mount them but it really wasn't a big deal.
Yes you keep your halogen high beams, it's just a splitter that taps into the high beam wiring to get the signal to activate the solenoid.
I've broke a lot of those clips on many cars now, mostly because they were old and I don't think you should have a problem on yours since it's newer, auto parts store has them for a cheap price if you should happen to snap a couple.
As for the alignment off, I had no problems with the horizontal, but when I first put them in, it looked like the projector was pointing up to high so to solve this I put a few washers between the screws on the top. When it was all back together I only have to do minimal vertical alignments.