If he encouraged you to give up your job then presumably he must have reassured you that together you would manage financially.
The fact he's now effectively using this as a stick to beat you with is disengenuous and actually rather cruel. Similarly, to urge you to take on the responsibility of a time consuming dog is irresponsible and unfair. I have the feeling that if he can spend at least £100k (FFS) on kids' parties, yet can't spend a fiver or so on an egg, that even if you did return to work, it would never be enough for you to be seen as, and therefore treated as, an equal in his eyes.
What the hell his ex wife has to do with "approving" his transactions god only knows. Either that's a (stupid) excuse, or, if true, an extremely unhealthy state of affairs indicating that either he's not let go of her properly, and/or he is scared to draw up appropriate boundaries now they are apart, which is sounding great big alarm bells for the future.
I too would feel like a skivvy in your shoes. From speaking to a lot of 2nd wives and partners, I am convinced that there is a breed of newly separated man who can't exist wwithout a woman - even though they aren't anywhere near ready enough emotionally for another relationship. Instead, the poor woman concerned fulfills his basic needs and, perhaps worse than that, is very often used as a cleaner and nanny, taking on the lion's share of the housework and childcare.
I don't know if this is the case with you ...... after all, with no money worries whatsoever, you'd have thought that "staff" could easily be bought in, yet the fact remains that you are being treated dreadfully disrespectfully. I'm sure you don't expect anything like £100k lavished upon you, but when he's spending that much (several times over) on his nearest and dearest - but zilch on you - then you're obviously going to wonder if you're regarded as "nearest and dearest" at all.
I'd be thinking long and hard about what you get out of this relationship.