There's a lot of interesting contradictions when it comes to Emet-Selch which is why I consider him to be a fascinating character. He fully intended to sacrifice Garlemald in the name of the Rejoinings but there's subtle things such as this:



Which serve to convince me that he was conflicted by it in the same way as how he didn't necessarily want to confront 'Azem' but had to if he wished to succeed. His treatment of Varis mirrors his treatment of Elidibus and Lahabrea who in all three cases are very much a reminder of what he has lost.

His efforts to try and live amongst the Sundered did appear to be genuine, though - so I do think there's a good chance that it was his son's death that burned any bridges other than the Rejoinings. I hope we learn more about Solus' wife and son in the future, even if it's just a paragraph in a future lore book or side quest.