1.) The slides all stick out a small about due to the bulb seal getting compressed and sealing. They do not close flush.
2.) Not sure about the crack. I don't think it should crack, but is it going to be a bigger problem? No idea. Worst care is that it "could" lead you down a train of thought that says the slide isn't quite level or square and as such tilting back and resting too much on the roller...but it may be a common issue (like the stress cracks in the outer walls on new the new laminate wall 5th wheels) with the 3612s. Hopefully someone will chime in. You may want to throw a call in to CR Customer Service.; they've been very helpful for me.
Honestly though, I don't know to what degree that is an issue.
2013 Elevation 3912
2017 Dodge RAM 3500HD Dually with AISIN
2014 KTM 1190 Adventure R