1.When you say faces, do you mean triangles? because you should always use triangles when talking about polygon count. The game shouldn't have too much problem with a 7k mesh (triangles), the only minor problem you'll get is "vertex shading not supported" message if your model has section with more than 500 vertices.
2.My experience is kind of limited, but i think what we did for the AT-TE was to keep every action within 100 frames and simply told the frames file where each sequence was located, the AT-TE didn't need much besides a walk cycle and death. If you go over 100 you'll probably need to create different .xsi files and merge them with a .car file to make the final .GLA.
Just a heads up:
If you are using Max 8, it's possible the export plugin is broken and prevents the .GLA from working in game. This problem happened when trying to merge new character animation sequences with the old .GLA, it simply won't work unless you are using an older max version with correct plugin.