Hi,
I have seen several workarounds to eliminate the fade.
The one I use is to green screen the title and overlay it onto the clip using the green screen feature of iMovie. To do that I drag a green background into the timeline. Take a screen shot of it from the preview screen (CONTROL-SHIFT-4, then drag select). That leaves a green JPG on your desk top. Double click on it to open it in the Preview app on your Mac. In the preview menu, go to Tools/Annotate/Text. A text box will appear in the green screen, that you can position where you want. Type in your text. Save. Drag into your project. Place it in the timeline-well above your clip. Then apply the green screen effect by clicking on the overlay icon (the one that looks like overlapping squares) in the tool bar at the top of your screen. In the selection box that appears below the icon to the left, choose Green/Blue Screen. Click the blue reset button on the top right of your screen to apply your settings. That should leave you with a non-fading subtitle.

As I said, there are other ways to do this. The freeze frame method will work with your version. You just need to make the title in another project on a green background, share it out, drag it back in again, and then apply the freeze frame to it like you would any other clip. After applying the freeze frame you trim back the fades on each side of the freeze frame, share it out again, and drag it into your original project.
Hope this helps.
-- Rich