I would have the battery tested to see if it has a dead cell first . Some times this will happed especasly if its over 4 or 5 years old and if it was left on a cement floor during storage witch will conduct electricty and damage the battery If the cells are OK in the battery then start checking the connections to the battery bolth posivite and negitive to the battery . If it worked before storage there is realy no reason it shouldn't work after storage . Also look for mice damage the little bastards will eat anything in the winter including the jackets off your wires so look for signs of then Good luck with it
seems impossible to me unless it has a hot wire connected directly to the batter. You could put a toggle switch on it and it should not drain the battery
ESP will communicate with steering angle sensor. You have pulled the fuse for the ESP system so it has lost it's base settings. It will clear once it has re-learnt. Try turning ignition on then steer full lock to full lock to give the system chance to relearn steering angle parametres
