Sous vide bath cooled after reaching cooking temperature, still safe to eat

Anything you salt will firm up in texture over a period of time. I suspect that since you cooked these with seasonings and then chilled and left them in the fridge before reheating an eating they firmed up a great deal in the fridge.

If you check out this blind tasting conducted by Dave Arnold at Cooking Issues you'll find some more detailed info about this topic. The gist of it is that for cook-chill-reheat purposes you shouldn't salt the meat before searing. For cook-direct serve meals your just fine doing it that way.

http://www.cookingissues.com/2011/10/12/to-salt-or-not-to-salt-thats-the-searing-question/

Whole salmon simply isn't a great candidate for low temp cooking in a water bath. While you can achieve excellent results with portioned salmon, cooked at 50C for well under an hour, this timing is impossible for a whole fish. It would be necessary to cook much longer. The problem is you would probably have to cook the whole fish for a couple of hours. This causes the enzymes to break down the flesh and you get a mushy, unpleasant product. Alternately, as you experienced, raising the temp to speed things up results in a dried out product.

I would choose a different cooking technique for the whole fish...or portion your salmon into steaks or fillets and look here: http://www.chefsteps.com/activities/sous-vide-salmon--2