Sounds like you have a fair amount of surface agitation causing a lot of "micro splashing" if you're getting dried salt crystals everywhere. That could be part of the issue.
I've got a 46g, with a semi-glass top (split glass top on plastic sliders, so it's not really air tight) and I see anywhere between 1/2 quart to 1 quart evaporation a day, depending on the room conditions - just to give you a comparison. If you've got salt everywhere around the top of the tank, it sounds like it's pretty open on top (which you want) so I'd expect you'd get quite a bit more evaporation than I see... so your numbers don't seem excessive in my opinion.
Evaporation is something you have to keep on top of with frequent fresh water top offs. But a gallon a day doesn't cause that drastic of a salinity swing - for a 40 gallon tank at SG
1.0250, if you lose 1 gallon of water through evaporation and don't replace it, your SG
is only raised to 1.0256. Granted... you want to keep it consistent, but in my opinion that little of an increase over 24 hours isn't that much.