My H used to have a 645. Two sports seats only in the back - and the reason we traded it was because our daughter would be out of her group 0 seat at some point and there was no way we'd have got a group 1 in the back!
So presuming the 635 is similar (is it same body but with a 3.5 not 4.5 litre engine?) I'd be unimpressed that it couldn't be used with the whole family.
I'd also be very sad if my husband did this... He has his own money, decides his own cars, but we talk about what he wants (and vv) because - well, because couples do talk about what they're up to. He'd never buy a car without chatting to me about it - not getting permission, not even for my opinion - but just daily chit chat.
Tbh, I'm confused by your posts. You start a thread saying you're really angry, but you really don't come across like you are. Sounds more like you like the sound of the car, and are quite enjoying the drama.
As to the amount of money... If the 30K was partly yours, it's out of order. If it was one time only money earmarked for house (inheritance, ISA maturing, equity from previous house) then I'd be seriously angry. moreso if it was for large scale much needed renovation. But if it was savings built up over a few months and was only needed for a new sofa cos you fancied one, not needed it, and could be saved up again, it's not such a big deal.
I'd still find it odd that my husband didn't want to talk about it with me though.