Good post. Have you try rest longer. I'm doing an accumulation training for my bench days. 10 X 10 and my first set after warm up was at 275 and the last one at 255. Of course, I wait 3 minutes between sets. You may need to do the same and wait longer than a minute if you want to increase the weight. Also a good spotter to unrack the barbell and don't waist energy in this manner.
Nice excel chart!!