I can't get the RAM Modeler view to scroll far enough to see edges when zoomed in. It cuts of my gridlines on the farthest sides unless I zoom out all the way. How do I fix this?

Try adjusting the window aspect ratio (i.e. window, not full screen).  Adding an extra grid slightly beyond the edge of the structure might also work. 

I tried adding grids outside my area like you suggested, but for some reason the won't show up anywhere. I made sure to select them but that didn't help.

If you have more than one grid system, make sure the system with the new grids is turned on (Layout - Grids - Select)

I figured out the problem. I had it selected, but my new grid system only had one gridline in it and RAM didn't like that. Once I added in all 4 bounding gridlines, they appeared.

Had the exact same problem, mine got it fixed when I saved the work, exited the modeler and started the modeler again.