The form looks fine to me. If this aweber form looks the same now even when you change to another theme then this is probably the way the form is intended to look like (since the aweber form generates its own css stylings).
You can try to use css to make the font smaller. Example:
.af-form-wrapper * {
font-size: 95%;
}Note: the previous version you’re using (1.0.9) is 10 versions behind the current one which you updated to. With such a huge jump some irregularities are to be expected.