I selected my broker account in the Montage window so I can trade, but when I enter another ticker on that Montage, it then automatically switches back to the demo account. Is there any way to make it not do that?

You need to set up a default account: Setup>Order Template> Account> “Apply this Setting to All Exchanges”>Apply. Then go back to the Montage window and left-click on your “TMP” button to load the settings. For more information, please see: https://dastrader.com/kb/knowledge-base/how-do-i-choose-the-correct-account-to-trade/