Sorry, just saw your post.
Vaccines: Eastern Equine Encephalytis, Western Eq.Encephalytis, Venezualen Equine Encephalytis, WNV, Tetanus Those would be the core vaccinations due to the risk levels. Influenza and Rhino pneumonitis might also be recommended depend on what you do with your horse and what kind of exposure to outside horses he has.
Anhydrosis is the condition that you are thinking about where a horse stops sweating. This condition isn't fully understood. There is a possibility that it's due to overwork of the sweat glands, but it could be several other things. The best thing you can do is to make sure your horse has plenty of water at all times, you don't work him too hard during the worst heat and watch for any signs that he is sweating less than usual or than you would expect.
Tying up can occur for multiple causes as well. Some of them are related to electrolyte imbalances, overwork, etc and some are related to a defect in the body like Equine Poslysaccharid Storage Myopathy. Feeding a balanced diet, supplying plenty of water, not overworking your horse all will help minimize the risk.
Licensed Veterinary Technician