magento invoice changes

I need the following changes on my magento1 store: 1. Set up tax rate 19% 2. i have a invoice extension where i can change the text and style of my invoices. I need it to split the invoice into 2. First part should list all products except the products from a certain category. Then it needs to show the tax and subtotal. The second part will show the category were all products don't have tax. again it should show the subtotal of all those items. At last there should be the part1 and part2 calculated together and show as the grand total. 3. I had done so many changes to my shop that now a very important part is missing. when you click on "create invoice" there is normally a box where i can add or subtract a certain ammount of money. This box is missing and i need it back ( see screenshot / red arrow - disregard the comment in the screenshot).