Is it permissible for me to take 95% as withdrawal fees from my partner’s profits, with a prior agreement that the distributed profit ratio is 50% for each of us, and that the withdrawal fees range from 5% to 95% and I am the one who determines them?

If the capital owner gives you his money to trade with it on his behalf, then you are a partner with your labor, and he with his money, and the profit is split equally; this is a Mudarabah (profit-sharing) contract. If you participate with both your money and your labor, this is a Musharakah (partnership) contract. In both cases, you are obligated to give him his agreed-upon profit without deducting withdrawal fees, because stipulating payment of withdrawal fees is prohibited, and it is consuming people's wealth unjustly (eating money by falsehood). If the withdrawal fees are of an unknown percentage (from 5% to 95%), this invalidates the Mudarabah and Musharakah contracts, because it leads to an unknown percentage of the partner's profit, and it is considered consuming people's wealth unjustly and clear oppression. Any condition that leads to an unknown profit in Mudarabah or Musharakah invalidates them. It is not permissible to enter into an invalid contract, and it is obligatory to cancel this invalid condition and beware of consuming people's wealth unjustly.