Yes, because max doesn't allow you to use multiple lowpoly meshes, you'll have to set up the keyframes in sub-object mode. It helps to move the objects numerically with easy to remember units like 1, 2 or 5 so you can come back with the highpoly and make the same adjustments. Yep, looks much better, you can probably get…
You should look trough this thread, covers most of your questions. http://www.polycount.com/forum/showthread.php?t=81154 When it comes to the cage, you should not have to tweak it manually just push it out. Layering bakes is not necessary either. For that problem area, unless that part of the gun will be seen up close,…