For the third door, use the corresponding number of each of the alphabets, so E is 5 and I is 9. Add for X and T so X is 2+4=6 and T is 2+0=2, so the code is 5692 :)
Ekskon is planning on reporting The Florals to the police, so if you leave the painting with Bosgye, the police will recover it when they raid the warehouse.