Inoculation size and stickiness

How much starter[leaven/inoculation] is too much given gluten[protein] content in the flour? Im adding 400g of starter[200g flour/200g water] to a mix of 800g of flour and 500g of water. Protein content is 13%. Is that too high inoculation? Seems that all my dough get very slack with little rise in 4h window period, despite signs of activity and big bubbles coming on top or sides. It rises more given enough time, but the dough get too slack, it would not hold shape when taken out of BF box or banneton. Gluten is properly developed by 15 minutes of kneading, lamination and two coil folds. Starter doubles in 4h. I thought it was too proteolytic so i fed it few times with high ratios and then left in fridge, but it haven't changed anything :(