Sounds like what you need is render frames. Render frames became possible in version 1.3.5, although I would recommend 1.4.0 RC3.
No, this is a different matter. I am new to Scribus and I am already working with 1.4.0 RC3. Render frames indeed are a superduperhypersopihisticated thing which I appreciate immensely. Indeed this was the most impressing feature of Scribus which made me a fan of Scribus on the spot!
No, I also need TeX renderings inside running text. I could use a small render frame and place it between the text later, but when I modify the text later, I would need to move all render frames to the places where they belong. This would be a horrible task to do.
Please see the wikipedia page to understand what I mean.