Hi,
It looks like you are not using any tables in the design, you have laid out everything without tables and the width's of the text boxes etc are a fixed length.
You should take a loook at this article for some design tips: http://office.microsoft.com/en-us/help/HA011227811033.aspx
If you use layout tables this will help a lot.
Typically if you use layout tables when you add the control to the table (text box, drop down etc) you let the column width of the cell in the table control the size of the text box, drop down etc (width is = 100% rather than a fixed width). This should help with changing the overall width of the form so it takes up more space.
We do offer an InfoPath detailing service (http://www.qdabra.com/en/consulting/detailingService.aspx) you might want to consider getting some formal advice from us. I see a lot of things in the schema of your form that are going to cause you problems later - for example using the name convention for your fields like you have (Field1, Field2) is going to cause you big headaches down the road when you try to figure out what data those fields are holding.
Hope that helps, let me know if you want to talk more about our detailing service and what you get with it.
Ted