I was going to state lower water (or increase sodium slightly) but you have done that. I wouldn't usually recommend so many different things but because you are having such an issue and over a long period instead of just adding in 1 and seeing the difference just attack things from different angles and each could benefit your training, pumps, fullness and hydration levels.
Firstly, I would recommend a balanced meal preworkout so protein, carbs (fast and slow) and healthy fats and please include 1 large (or 2 small) banana to that meal. If you train higher volume I would recommend 1 preworkout shake and 1 intra shake that you sip on throughout training. If you are not training high volume you could just put most of this in preworkout and that would work fine.
Anyway 5g taurine pre and intra workout, 5g creatine monohydrate and 6-10g citrulline malate preworkout (could half pre and intra if you want). If you are training higher volume include some hbcd's (or similar) with eaa's. Glycerol (glycerine) is fantastic for hydration and what you need and I would recommend adding that in. Pretty much the more you can do the better especially if you are consuming a lot of water. The sky is the limit and in studies doses such as 100g are used so nevermind the 3-5g you get in some BB supplements so push that if you want and use at the very least 10g and that should really improve things.