Yes, come back and read this thread when he is being fake-nice.
When you leave, it will go something like this, so please be warned and baton down the hatches.
phase one, Pleading and niceness, please come back, I do love you, it'll be different, empty promise empty promise, dangled carrot blah blah blah
phase two getting abrupt with me, his irritation that the niceness not working clearly showing, frustration and impatience that I wouldn't return to heel, crescendoing in to phase three
phase three losing his temper with me, a naughty disobedient child. Erroneous and unfair accusations (gold digger, it's all about money, you're so selfish, you're so impetuous, you're breaking up the family, this will be on your conscience forever) awful awful character assassinations, putting me on trial and making me defend myself to him
phase four a bit of remorse, but really, guilting me. Did you know that guilting is a verb? well it is. Guilting me in to feeling responsible for the children not having two parents under the same roof, making me responsible for HIS happiness by telling me I'd destroyed him, I'd ruined him, he was devastated, he was a wreck, I was cold hearted, I was selfish, what had I done to him,.....
phase five Realising it hadn't worked and that I was even more determined not to return, so a calmer phase, while he had a bit of think, but he had nothing new to offer, so rinse and repeat phase one again ...
I had to endure this about four or five times. So brace yourself. He will not want to see his prize (you) his deposit (in your bank account) his lackey (your labour) walk away. He will fight that.