1) I'm not sure what you mean about credit card validation. Do you have "Validate credit card numbers at checkout" selected at admin/store/settings/payment/edit/methods? It should respect that.

2) Do you mean that when you press enter in one of the credit card fields it executes a "click to calculate shipping"? This would be because that button comes first on the page, so your browser submits that button when you press enter. No way around this that I know of, other than some fancy CSS or javascript work... but maybe I misunderstood your problem.

3) For adding the total + shipping to you cart contents pane, you just need to add a function phptemplate_cart_review_table($show_subtotal = TRUE) to your template.php. You can copy and paste the standard cart_review_table into there and then tweak it...add a couple rows to the table with the extra info you need. If you want it to dynamically update with shipping selection and tax based on the state, you'll have to figure out how to integrate it with the javascript used to handle those updates. Shouldn't be too hard, i don't think, but I haven't tried it yet...