Sorry, we don't have any way to specify the order of checkout buttons shown in the cart. You might consider adding instructions to the cart by adding these lines to your View Cart code on every page, just before the "// -->" line in the standard code you got from Seller Admin:
function EJEJC_config() {
EJEJC_POSTCALL=true;
}
function EJEJC_shown() {
jQuery("#tdPmnt").attr("innerHTML",
"<b>PayPal buyers:</b> please remember to click the Pay Now button during checkout to complete your payment.");
}
We also do not have any way to pass a buyer's name and email from your site to the Authorize.Net checkout page.