Hi,
1. and 2.
Having a guest checkout would help. Turn off the "login" setting and set the "registration" setting to "guest" in the Checkout tab of the HikaShop configuration and the interface will be simpler.
Also, disable the address custom fields you don't need to reduce the amount of information to enter.
You could also remove the "address" view from your "checkout workflow". Since the customer has to enter his address each time in guest checkout, he won't need to select another address and manage his addresses.
Note that you'll want to delete the user accounts from the Joomla user manager so that people can guest checkout with their email address.
3. Add the code:
if(!$this->step)
before the line:
echo $this->cart->displayButton(JText::_('CONTINUE_SHOPPING'),'continue_shopping',$this->params,JRoute::_($this->continueShopping),'window.location=\''.JRoute::_($this->continueShopping).'\';return false;','id="hikashop_checkout_shopping_button"');
in the file "step" of the view "checkout" via the menu Display>Views.