Dear LouP,
Your OP made me cry.
You are amazing, and so is your mum. When my exH left me and my 3 dc for my friend, I was hysterical. I played right into his hands, because it wasn't quite as easy or as rosy as he thought it would be, and he constantly played little games to ensure I was still available should he change his mind.
I honestly believe your ex does still 'love' you, and he may also 'love' OW, but he is keeping his options open. After acting in such a decisively cruel, callous fashion, he is making sure he hasn't entirely burned his bridges. She probably laughed/got a bit freaked out when he turned up with half your home, and the chutneys (!) and they may have had a word or two. Seeing that things may not be entirely harmonious, and with both of them realising the magnitude of the devastatingly shitty thing he's done, he's making sure his conscience is eased and he's secure either way.
I am sorry I'm so cynical but this kind of thing happens too often.
I understand your need for details, I really do. I would want to ring his boss as well. I am still finding out tiny bits of what was happening in my marriage whilst I lived in suspicious ignorance, and that was over four years ago. But the one thing I wish I had done when he finally pissed off was act with dignity, and ignored him. My biggest regret was the degrading way I begged and pleaded with him to love me again (shudder), and questioned him continuously. My biggest moment was emailing her (wealthy) husband to ask how long it had been going on for, and he cut her divorce settlement in two. Turned out he was unaware of the affair, and the vile, sneaky duo were holding out for the money before they announced it to him and her DC. Not nice of me, but then again not nice of them, either. Nothing good or nice can ever happen in these circumstances, and everything becomes grubby. Might be best to keep out of it where possible.
You've had some excellent advice on here, and you are being amazing. We're all rootin' for you! There's a long journey ahead, lots to sort out re finances etc, but no point in crossing that bridge yet. Get yourself strong first - that will take time but you have wonderful parents who seem as though they'll be there with you, as will all of us!