First off, I doubt he has permanently, definitely left. Sounds like just another rash, feckless, selfish, manipulative action in a long list.
But ...
this time last weekend, we were ok
No offence, op but you weren't. You'd already separated this year due to his behaviour and he was supposed to be back on his best behaviour, making an effort - yet he couldn't even get to the end of the year without doing something like this; disrespectful, sleazy, verging on cheating (to me anyway), irresponsible, hurtful, shitty, money wasting (money supposed to be for your family home deposit) etc etc.
Followed up by lying, gas lighting, manipulation, suicide threats, and now walking out on your family.
How did you even find out about the two 200 quid withdrawals? Did he tell you before you found out or would he have covered it up/lied by ommission if you hadn't realised?
He was clearly acting really poorly for a while or you wouldn't have separated; especially given how committed you seem.
His attitude towards relationships, marriage, women, honesty etc etc is really shitty; not sure how any self respecting woman who is award of how he acts could make it work.
His text about feeling sorry for the kids .... That is nauseating, enraging hypocrisy a d irony.
I feel sorry for kids whose dad soebdx hundreds of pounds of savings intended for a deposit for a home for them on private nude "dances" and drinks for him and his friends in seedy, sleazy strip clubs - oh and "loses" significant amounts through carelessness as well (not that I'd believe that).
I also feel sorry for kids whose dad is so moody and shitty at home that his wife, who is clearly invested, commited, sincere and doing her best is pushed to separation
I feel.sorry for kids whose mum is totally naturally upset & angry at their father's shit behaviour, which affects her parenting, no matter how hard she tries not to let it.