I thought I had all the config changes right, but the button connected to MCLR doesn't work (well, at least the display doesn't change so I'm assuming the interrupt isn't being fired) and the LED just stays on - no blinking.
I'm confused....
Your code sets up DT-Ints to use INT_INT as the interrupt source for your handler but you say that you have the button connected to MCLR (RA3) which is not the INT-pin. RA3 has Interrupt on change capability and the comment at the INT_ENABLE says you're enabling IOC interrupt but you aren't.

I'm pretty sure that you don't need to (or even should) set the GIE or INTE bits when using DT-INTS, it handles all that for you via the @ INT_ENABLE macro. You also don't need to clear the interrupt flag in the handler since you've asked DT-Ints to do that for you.

/Henrik.