The new TELUS TV Digital Box has a screen reader built-in, leveraging the Android TV TalkBack service. You can turn this on by navigating to Settings --> Device settings --> Device Preferences --> Accessibility.
There are also other configurable accessibility settings here, including closed captions, where you can change the text size and colour/background combination. You can also enable High-contrast text, which highlights the font in the user interface.
I will pass back the feedback about guide font size to our development team, but hopefully the screen reader and font contrast helps a bit.