Predictions for how Chapter 5 will go:
I don't think Toby will make Asgore and Toriel get back together, assuming Asgore even lives... but I still do think Chapter 5 will have Asgore have his moment and be the tipping point where a lot is revealed.
I imagine Asgore DOES reveal the truth to Toriel to somehow, which I'm assuming is that he was framed/took the fall for Dess' vanishing. Maybe he just took the blame cause he failed to find her as police chief, whatever, but he was blamed. Carol (and maybe Rudy) know the truth which is why they're so kind to him despite it, with Carol hiring him and paying his rent, as a way to make up for him taking the fall.
So, he ends up revealing this to Toriel, expecting her to get back with him... but she declines.
She explains how that was just the straw that broke the camel's back, their relationship was already on the rocks, such and such, even if it wasn't his fault Dess went missing, they were gonna divorce anyway.
Gives Asgore a chance to get his moment without putting them back together.