is there a way to shrink the height of that to the height of the send button? even better a single line of text?

You can reduce the size to that of the Send button by dragging the gap between the typing area and the conversation area.

And you can make it even smaller if you hide your Display Picture.

i understand aboutthe DP and the bar slides but when i click the double arrow to drag it it wont let me move it past where its at.

took a screenshot of my convo window  and the left is where its at and wont let me move it from and on the right is where i want it to be.  i like the minimalist style  and the borders around the windows are too thick for my style. i also wish i could get hide the section at the top of the list window  also that has the DP and nick and all but i dont see any way of doing that

Looks like the only way you're going to get the typing area that small is by using a skin.
Either that, or use PE Explorer or similar and take a peek at, IIRC, UIFILE921.