Hi,
1. I think that you'll probably find your answer through that:
In the Business edition, you have the menu System->Emails where you can customize your emails. There, you can easily publish/unpublish the emails in one click.
Or :
You would have to edit the hikashop_config table via phpmyadmin and change the entry order_creation_notification.published entry to 0.
In your case you'll have to unpublish the "Order creation notification".
2. There is an option for that, in Configuration > Main > Product, enable "Update the product stock on confirmed status".
3. The customers can see the created order thanks to the HikaShop menu "User control panel", then you can enable the option to allow payment of order later in Configuration > Checkout.