Consider this a crash course on why 'hotlinking' is bad and why you should feel bad that as a 'game developer' you think it is ok to use that as standard practice.
There's a way to embed it properly or host it yourself as a fallback. It isn't itch's job to permit hotlinks from their CDN for you or anyone else.
Also iframes within iframes within iframes is such a screwed-up system that you might be learning gamedev for browsers from some book made for Internet Explorer 6 back in 1999. Time for you to learn HTML5 and the proper way to do game embeds from the itch platform.