OP - I can't believe that deep down you don't already know that you're being taken for a ride. Maybe you were carried along with the romance and excitement of it all in the early days so you buried any misgivings ? But this is awful and there's no logical or acceptable explanation for the way you're being treated.
You saying you were "lucky" to find him "at all" makes me wonder about your self esteem. Do you consider him to be "out of your league", or have you not had much past luck with men maybe - have never had anyone want to "commit" to you before ? Because otherwise, I don't understand why you've let yourself be treated like this ?
The toys in the attic is a bit of a red herring but nonetheless, regardless of how much they're worth, if he thinks (or likes to boast) that they're worth anything - even hundreds - he should bloody well be selling them pronto so he can at long last contribute something to your household. The fact he claims they're worth "hundreds of thousands" no matter how delusional is a fucking insult under the circumstances. How dare he (potentially) be sitting on a fortune like that and in the meantime let you pay for everything ! You even enable him to see his children while you can't afford to have any yourself (though please please don't even think of doing so with such a selfish man). Any normal, decent person in financial straits would do all they possibly could to raise money if they had to depend on someone else for their keep - I mean, who the hell does he think he is ? He obviously has a hugely inflated sense of self importance/arrogance if he thinks you should be somehow bloody grateful for the pleasure of subbing a grown adult. Yet you come across as "grateful" anyway ..... I suspect, sad to say, that when you met he saw you as a means to an end, and can't believe his luck.
Toys aside, before you even knew about them there's something much bigger going on here. Like everyone else I'm at a loss to understand where his pay's going. He might well have a private arrangement with his ex over maintenance but it's ridiculous to suggest that all of his wages are going there. Where the heck is the rest of it going ? .... do you see or have you ever seen his accounts ? I'd guess he's either squirrelling money away and/or has some sort of secret habit (gambling, drugs). Or, and perhaps this is arguably worse, does he blatantly spend money on himself (socialising, clothes, hobbies) whilst claiming he "can't afford" to share any of the bills - and you've let him get away with this.
A "few bottles of wine" is another fucking insult. It's a sap .... "oh look at me, I'm treating you". No, he's holding you in contempt.
I'm really sorry OP but anyone whose first reaction is to threaten to go to his mum's when you make a completely reasonable request isn't that invested in the relationship. Maybe, just maybe (and this is giving him huge benefit of the doubt) he'd "forgotten" his stash until you mentioned your CDs - but if so, he'd have immediately started to make enquiries about selling it - not making stupid excuses and getting angry with you.
What I also don't understand is how he was living before he met you ? Was he at his mum's for free ? ..... did she buy all his food and slip him money for treats like going out and holidays as you have done. If that wasn't the case then he has a sum of money over every month which isn't accounted for. And if it was the case then more fool her and it doesn't mean that he's entitled to leech off anyone else stupid enough to be taken in by him.
I know that all of us harping on like this can't be a pleasant read - and you're probably already in shock from realising a solution (in part) to your money issues could be staring you in the face yet he won't facilitate that, but please please do something about this. Don't let him drag you down any further, don't let him prevent you from having the opportunity to live an honest life without any secrets and stuff that doesn't add up. I really think you should be getting legal advice re: your flat and what he may or may not be entitled to in the event of a divorce so you know where you stand - and then maybe, just so you can tell yourself you've tried absolutely everything, you confront him again and have a warts and all conversation about money and bills and who pays for what, and what he earns and where it's all going. You need to see his statements - don't be put off with airy-fairy comments about "lots of maintenance". I do somehow suspect however that he'll be very reluctant to have a full frank and fair conversation about money with you because any move towards a fairer system is going to disadvantage him (in his opinion) and I wouldn't be surprised if he blows up at you again.
At which point you'd be doing yourself a huge favour by telling him to fuck off back to mummy's - if she'll have him - I hope she doesn't. Cut your losses now because the longer you remain married to him the greater his claim for any of your flat will be. Hopefully, though I'm not a lawyer, in the event of any dispute, his claim should be minimal anyway .... he's made no contribution, and presumably you can show - for example - no money being transferred to your account from his, all the bills in your name and so on. And of course he can't claim he was making a non-financial contribution to the household, e.g. by being a SAHD. Even if you did end up having to pay him something the relative shortness of your marriage should mean it'd be minimal - and that would surely be worth it to save £££££s in the future if you carry on as you have been ? AND, you'd also get your freedom back and the chance to work on your self esteem, the chance (when you're ready) to meet someone decent, and month on month you'd be so much better off as well.