Here are some considerations: investigate other protein powders as you may have a reaction to the artificial sweetners or fillers used for the brands you have tried; let us know how much time you have to cook (example you may only have 2 hours on the weekend to cook in bulk); and your budget...
You can consider adding in any of the following movements to get past a sticking point: isometric pushes (such as bench pressing in rack with two sets of pins closely put together so you can press the bar into the upper set of pins at the top end of your sticking point), static holds (again, do...
One thing to also consider is working the "extensor" muscles of the forearm which line up with the outside of the elbow. A cheap way to do this (borrowing from minor league baseball pitchers who usually don't have much money) is to take a thick rubber band and place it around your fingers...