Didn't read the other posts, so forgive me if this came up.
You need one exercise to build your Deadlift grip. Stand with a weighted bar with a standard double overhand grip. Stand in that position for one minute. Do three sets each lasting one minute.
The weight should be so heavy that the one minute is a real challenge. Do this three times per week and advance the weight when it becomes not so difficult.
Your problem will be solved in one month...or your money back.