Unlike most modals, you can customize the look and feel to your heart's content. You can also implement as an iframe to give you further control over the user experience (including adding other info fields) for donors.
The modal design is purely subjective. I think they did a fine job. It's great for the purpose, because it's uncluttered, has clear prompts, and has useful placeholders. IMHO, anything else would just be fluff that gets in the way of the UX.
I missed those the first time around, because my gaze was focused on the form and it's container. You're right, that should be addressed. I would imagine addressing the scroll bar issue would resolve the cut off text as well. It looks like something that wasn't a priority for roll-out, because it doesn't really affect UX so much, but I do think it's something that needs to be fixed in the next release.
(I have scrolled a bit with my mouse wheel to reach that state)