I'm on a 1,500 mg a day sodium diet as well (for a vestibular disorder). We just went in August. Honestly, it was hard.
I ate a protein bar and a glass of milk in the room for breakfast. For lunch in the parks, I had a Kids Mickey Check meal because those have a sodium cap and they do have nutritional information available for those and you can kind of figure out how much is in the various components. Around 3 pm, I would be starving so I ate a Mickey Bar every day because those are high in calories and low in salt (one plus lol)
Then for dinner, we ate TS. I would tell the server when we got there and the chef would come out. The chefs were great and would come out and would really try to help, but the selections were very limited because so much of the food is pre-seasoned. I would usually order a steak with no seasoning and they would cook pasta or potatoes on the side with no salt. I had a side salad every night but I had to use my own no-sodium salad dressing packets that I brought with me because their dressings are high in sodium.
Two nights, my husband ran out and got Five Guys because their burgers are low in sodium (I use my own buns) and you can get the fries with no salt and the potatoes are cut fresh in the restaurant.
People say Disney is great with allergies, and that's wonderful. But they aren't that great with sodium, even though the chefs try very hard to help. Good luck!