Create WP editable Price Form with multiple Quantity Formula

I need a fillable order form form my custom order form on my website www.theornamentcompany.com. The current form is dated, and need revised quantities, copy, and encryption for the submitted credit card info (which I will process from our land based office account-don't deed automatic credit card service). I would like to have this form updatable on my word press site so I can change prices, add or subtract products, and update terms without a directly from my computer. Also, it needs to work on safari (which I use) and Firefox and Internet Explorer. The attachment shows how I need current form modified.