If I remember correctly and others here can confirm that... there is some notches on the frame to properly aligned and seats the brackets at their correct spot. That may be why you have such a gap. When I look at the space between your brackets and the frame it makes me think that when you hit a bump, the brakets may possibly tilt being secured with only one bolt.
If I were you I would correct that as soon as possible and certainly before going to the alignement shop.It can also be dangerous. There is a lot of pressure going through these brackets when you hit a bump. Maybe drill and tap ? Or it can be blown with air once properly heated with a torch at a local shop.
Is the LCA parts number are OK for your Murano ?
Can you describe more what you mean by sloppy/loose steering ?
Keep in mind that when a front-end is badly misaligned(i.e. after changing LCA) all sort of behavior can happen. For example, the left front wheel can fight against the right front wheel causing an inprecise steering or a wandering front end. Like you said, you can confirm your alignement has changes by looking at your steering angle.
Also, make sure your sway bar bushings are OK. But this would normally cause a noise or a clunk when hitting a bump. Certainely worth a check while you're there.
Is tire air pressure OK?
Once the wheel is off the ground, grab it at 3 and 9 o'clock. You should not feel any looseness or endplay when you shake it.
A last thing that comes to my mind is worn shock/strut.