If you go into the sample scene for "links", you can see some code there for how to convert existing tags to STM ones... (e.g. <link=myLink> becoming <e2=linkSpawnEvent> etc) That way, you can keep the system you have, and just convert it for the text renderer.
I think the "Auto Pause Full" feature would work well for what you're trying to do, but it's also possible to just manually take the leftoverText field, and send that to a new box when you continue, too... (I would advise this if the text gets *really* long! And look at the "pagination" scene for an example on doing this, too) STM is just a renderer, so you have a lot of control over how to integrate it into *your* system.