It is my belief that a large part of developing grip strength is to not use straps on anything for a while. I think, because of social media outlets, the concept of using straps is forced on individuals from the start (before any grip strength is really developed). Thus, the major muscles (back, shoulders, legs) develop strength far faster than the forearms.
Instead of going after the numbers and increasing your strength that way, try lifting what you can lift without straps for reps for a few months and just let your grip strength naturally catch up.
Do deadlifts (regular or stiff leg), dumbbell lunges, farmer's carries, row variations, front raises, laterals, and pullups/pulldowns without straps for a program's cycle (3-4 months ish) without using straps. You may not go up in raw weight, but you won't lose any muscle either...and your grip strength will surely improve.