Being an absolutely positioned element, the Tooltip tries to shrink itself (contrary to static block elements, which try to expand). If you don't want the content to wrap, the easiest thing to do is to simply disable this behavior with CSS.
The above will influence all tooltips in your application, so you may want to limit the style to particular instances only. To do this, use a different (custom) CSS class, applied to an element, which wraps the tooltip content. You are already injecting the content manually anyway, so half of the job is done.
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