Ok, so... been 18 months together yet he hasn’t introduced you to a single one of his friends or family members. In fact, when he was having a night with his best mates, he particularly asked you to make sure you weren’t there... but claims they definitely know about you.
Now you’re saying the reason you live with your parents is because you’re saving to move to France in summer 2022 (since that’s post-Brexit deadline 31/12/2020, I assume you’re a dual EU citizen or looking for a job offer, whichever, good luck), and there’s nothing wrong with any of that, but does that mean that he thinks he’s going to go on like this for another 18 months, keeping you in this separate compartment in his life, sneak away to France with you, and then just come back to the UK once a month? And the first time you’d live with him, and have him live with your kids, would suddenly be in a foreign country? Sounds like a complete recipe for a disaster, especially when he’s not putting any effort into your relationship right now.
Having a goal for 2022 is great, and it sounds like you have a good head on your shoulders, and if you plan, you can succeed at a lot, but a bad relationship can also derail so many dreams so quickly. And if it’s been a year and a half and he’s still “hiding” you for some reason when you’re a smart, compassionate woman he should be proud of (whose only BIG problem I see is her fear of confrontation - PLEASE Google and start learning healthy confrontation methods now because you’ll need them for France!), I think his Facebook is just the straw that broke the camel’s back. And unless he has a really good explanation (maybe he does?), it also sounds like you know it’s time to show him the door.