I can see why you're confused too. It took me a while to figure out some code that works, but I honestly can't tell why the width is being set the way it is. There's a span *inside* the Like button area that's set to 138px, and that's not being done (I don't think) by JFBConnect).
The following block of code in your CSS should fix it, but please test and let us know how it goes:
.jfbclike div span {
width: 450px !important;
}I'm glad everything else has gone smoothly for you!
Best of luck,
Alex