First it depends if your country is part of the North American Free Trade Agreement.

Your major broker in Texas should have a Tax Accountant, or Certified Public Accountant who assists him with filing the company’s and his US Tax Forms.

The type of tax you are asking about is the tax on retail sales, which is also called a sales tax. Every State in the United States has a different tax rate where the amount of the sale is multiplied by the tax rate, this amount is held in a separate bank account to pay the sales tax on a quarterly basis.

Paypal usually charges the sales tax and collects the sales tax.

Usually interest earned in a bank account in the United States is taxable income to a citizen of the United States.

When you visit for a month or two every year as a business trip to meet with your customers, I would suggest in making an appointment with a CPA Firm, (Certified Public Accounting Firm), maybe Deloitte and Touche, and speaking to an International Accountant who will be able to answer your questions their phone number is: 1 212 489 1600 or you are able to fax them at: 1 212 489 1687, or you may have a CPA Firm in your country you should be able to contact. I am an accountant but I am not a specialist in international accounting and if you would like you may print my answer and take it with you. I do not live anywhere near Texas.

Wishing you well and much success.

Your activity No. 2. You have an online business. Your customers in the U.S. send payment to your bank account in the U.S. through Paypal. To fulfill the orders of your customers, you take the help of a company in the U.S., which sends the coffee on your behalf to your customers.
This activity is business activity conducted in the U.S. You must pay taxes in the U.S. on all your income due to your activity no. 2. Your will need to file return in the U.S.

It is better that you consult a taxation professional in the U.S.
Also, depending on the law of your country, you may even have to report in your country the income from your activity no. 2.