Captioning in Storyline

I tried to post this earlier through Edge, but it hasn't appeared in the discussion conversations, so I'm assuming that it didn't post. Apologies if this appears twice.

So, I've created a software video that is launched through the Storyline player, and no matter what I've done to change scaling, change capture agent (I've tried Peek, Camtasia, Captivate and others) the output when played back through the Storyline Player is too blurred to be useful.

I've found a solution by launching the video, uncompressed, in a separate browser window from the player. You can see the settings I've used in my attachment to this note. And, now the playback is crystal clear.

However, my captions that display when the playback is through the Storyline player no longer appear - and this is vital to my audience for accessibility reasons. 

Is there any way for the captions to make an appearance when the video is launched in a separate browser window? Alternatively is there any way of exporting the captions in a format acceptable to other MP4 software - the Storyline caption format of VTT does not seem to be acceptable to other video processing software, they are all looking for SRT or other formats.

Apologies if I am being thick and have missed an obvious setting but any advice would be massively appreciated.