Instead of salt, take a few mustard packs (like Frenches). Straight table salt isn't the best electrolites replacement. Mustard has salt, vinegar, and most importantly Magnesium.
This is a old soccer coaches tip for cramping. It takes a couple times to get used to. I chase it with water or Gatorade (or Poweraid). I like to shoot two packets when I feel a cramp coming on.
I live in hot and humid Honolulu, and I've been using this method for years. And it really works! Do a Google search on muscle cramping and mustard. There are several posts about it.
Another choice is a small package of pretzels. It has salt and carbs.
If fluids are sloshing around in your stomach, you drank too much. Mile 18 in a marathon is the last time you should drink the whole cup. The body can no longer absorb fluids. So from 18 on, just sip a little to wet your whistle, and don't drink the rest. I saw several people puking up the excess fluids from Animal Kingdom on.
Bodyglide and Vaseline, you just can't have enough of it.
One last note: I had to laugh to myself seeing all the waistpacks, bags, armbands, hats, etc. all thrown on the side of the road. I bet all those people bought their new belts at the expo, without having ever trained with it. So from a mile or two from the start, there was a trail of new goods thrown out because they found it too uncomfortable. Always train with the stuff your going to race in. NEVER show up to the starting line with something brand new. Shirts, hats, clothes, shoes, underwear, etc. have to be broken in.