So first, you can not have someone sitting in a queue longer than 3 days if you want the email to send to them. They will encounter a triggeredsend expiration error.
Also answered in this stack exchange post
In the other part of your question, the entry source DE is not leveraged once a contact is injected, and is common that this DE is overwritten. ...
If you're using SmartCapture in your Cloud Page and you have Journey Builder in your account, this is pretty easy, but it does take a few things set up correctly.
Ensure the "Commercial Person" is in your All Subscribers list with a non-personally identifiable SubscriberKey.
Make sure your Data Extension is Sendable, similar to this one: