I will attempt to get this use case working and make a new AEM/SQL SERVER article that shows everything required here.

I have only ever used MySQL for the DataSourcePool use case.  I have SQL Server on my DEV Machine. I will test this out and post back. I would think this could be a DRiver File issue or COnnection String issue when you setup the configuration required.

MOre recent version -- Adobe Experience Manager Help | Creating Adobe Experience Manager 6.3 Sling Model Components

See this article - it will point you in the correct direction: Adobe Experience Manager Help | Working with Sling Models in Adobe Experience Manager

We have plenty of video and articles on using MySQL with AEM. See: Adobe Experience Manager Help | Querying MySQL data using an Adobe Experience Manager 6.4 DataSourcePool This will show you step by step on how to get this use case implemented. See the video too at the end of this article.

Typically each component has its own RTE configured - see:Configuring Experience Manager Rich Text Editor Plugins in a Touch UI Component Dialog

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When you say Template - do you mean the component code? Anyhow - if you want to perform this task in the HTL itself (I would recommend Java and Sling Models and use HTL as a view), - see: htl-spec/SPECIFICATION.md at master · adobe/htl-spec · GitHub

If you use a Sling Models with your HTL - you can use Java to perform all REG EX functionality.

This does not sound like a supported use case. Sounds like a hack and will not be supported by the AEM Cust Care team.