Hey. I've got pretty bad vision, so when I saw the walls of text this question was basically my first one, too. Since then, this is what I've discovered.
What you can do right now.
One of the biggest sources of text in the game is the bootypedia, and a lot of logs are listed there. Basically anything with the left and right arrows at the top left is a bootypedia entry. There's a searchable html version of the bootypedia included in the game. Just pop open the XPiratez folder, and unzip the xpedia zip file found there. Then, go into the unzipped folder and run the 'xpedia.bat,' and the searchable page will pop open.
If you type the heading (Larger words at the top of the text) into the searchbox at the top left, you'll get a selectable version of the text you can read with TTS.
What I don't think can be done.
Disclaimer: I know very little about the way openxcom works and am basing this off of observed behavior while I edited ruleset files. I may be talking out my posterior, and if I am, please feel free to correct me.
So, that leaves event texts. The problem here is that I'm fairly sure these, along with the bootypedia entries, are baked into the images every time the game runs. Escentially, there's no text for your TTS to read because what's on your screen when an event pops up is an image with words drawn into it, rather than an image with a text overlay.
What may be done.
I'm pretty sure all the event texts are located somewhere, probably in the languages section of the Xpiratez>user>mod>piratez folder. You could go in there and find the entries for them. Problem is you'd probably be going into a spoiler minefield. I just haven't bothered, since only having to worry about event texts is JUST enough eyestrain for me to handle.