For a museum that's under-attended, try the Musee de Petit Palais (though you seem to have hit the Pompidou on a slow day). I've never been in there when it hasn't been virtually empty, and it's quite a presentable collection - for any city where there is no Louvre.
As for cheaper restaurants, try the Left Bank, or the outlying neighborhoods (the 13th, and 14th, perhaps - the 13th is Paris's Chinatown, among other things, IIRC - the 4th is quite painfully fashionable at the moment).
Merci. And if by "painfully fashionable" you mean out west hollywooding west hollywood then yes, you are 100% correct.
Must have been a millionaire, or so it seems. Everything is twice the price.
Anything else anybody knows? Cool jazz clubs, classical music concerts? Hidden gems of restaurants? I'll be here for a while, so I have plenty of time to explore. And so as not to hijack the thread with useless crap, here are two more fits from tonight: