Thank you for your question.
Under the scenario described, since your company has nexus in Texas, you would be obligated to collect and remit sales tax for all Texas buyers.
To make it more complex, sales tax is calculated based on the address of the recipient. Sales tax here in Texas varies by city and county, above the state's base 6.25%
You are the seller of record on these transactions; Amazon is simply a distribution channel.
However, Amazon does have different sales models. If you sell WHOLESALE to Amazon itself, then you do not collect sales tax.
If you are the seller and Amazon is simply drop-shipping, sales tax must be collected.
In most cases, Amazon's systems are setup to correctly calculate sales tax even when a third-party vendor is the actual seller. Be sure to check with Amazon on how this is physically accomplished.
At this point, Amazon has reached sales tax agreements with almost every state in the union. If Amazon is selling product, they almost universally have to collect sales tax unless the buyer is exempt.
So this applies if theoretically the product is not being shipped from Texas to the buyer in Texas correct? I have decided to err on the side of safety since starting and have been collecting and remitting sales tax to Texas since I started, even with my questions, but learned other sellers are not, and just wanted to clarify the actual law! It sounds like you are very familiar with this and it is refreshing to hear from someone who has knowledge of this situation! Thank you!