It may be time for a new water heater instead of fighting with the old one... If it's possible try using a pipe wrench with a cheater pipe to get the defective element out... You may have to tin snip some of the outer metal skin to get it out of the way enough to get a good bite on the element with the wrench jaws... And all that sediment should be removed from the tank for the new element to have a long life... Good luck, kooler