The program stalling issue is caused by several things. First of all, this is a visual basic program which is not going to be as fast as say a C++ program. Another thing is that the program is actually run twice when it is first loaded. The first time is to determine its view extents, then it is actually drawn. Finally, computer speed is a big factor. If you're running windows 98 on a 300Mhz laptop, it's not going to be very fast.
I haven't run into the overflow thing, but I will try to figure this one out.
I'm not sure about any problems with the view window... Did you try setting your view to Isometric? Or try any of the zoom tools? Maybe a screenshot would be helpful in explaining the problem.
As far as 4th axis goes, this is probably a 'down the road' thing, unless I get inspired .