I've recently installed this application.
https://github.com/White-Tiger/T-Clock/releases/tag/v2.1.0%2357

In an attempt to get me to pay more attention to the time on my computer (ADD / ADHD)

Problem is, despite ticking the option to spread to other montiors, it's not working - is this DF fault?
Can someone else please test and or optionally, maybe just add (some) of the features of this app to DF?

(Much larger clock font / colours)

You can change your clock size and colour etc on your monitors that DF is controlling as explained here:

https://www.displayfusion.com/AdvancedSettings/?Version=9.1.0.0#taskbar_clocksize

Scroll through the sections to what is relevant to you.