Thanks for your reply. Let me reiterate what you wrote, so I understand you fully.
You gave a sending example, but you are recommending that I do not use it. Instead, I should "manually fill and send" to my users. Is that correct?
What is a "hot wallet"?
The example also shows the database going through pending sends. You would modify it to do a dry run to tell you how much to deposit then send for real.
A hot wallet is a wallet your server can send from, eg. The example BUT has funds. Keep it empty until sending.
Also watch out for a hack where they change your deposit address.