Textwrap is controlled by the TextWrap property of the textbox item. When the property is true (default value), it would wrap the text exactly as you need it. Currently there is an issue with it in HTML rendering, but the problem is that it always wraps, which should not affect you as this is what you are after.
Have in mind that in order to have the text wrap, the textbox item width should be insufficient to accommodate it and only then it would wrap. If its width is enough to display the text, then there is nothing to wrap.
the Telerik team