how do i change the font size and line spacing to fit in the space provided

You can see and edit the form field's properties by double-clicking on the field with the form edit tool active.  The appearance tab will include font settings.  For font size, there's one there called "auto", which will shrink the type as you ad more and more.  I'm no fan of this feature, but it does what it says.  You can also dial in a fixed size, which I prefer.

My best,

Dave