Why does the cat keep peeing outside his litter box?

Hi, my girlfriends cat has always peed inside and outside his box for many years now. I just moved in and I can not take it anymore. He is a 12 y/o male fixed cat. I took him to the vet and they said he had a ph problem in his UA and had a bladder infection. Ok fine, change the food, put him on antibiotics, and he still voids outside the box. Lately is has been on the sofa. I do though see him voiding as well in his box. He does have a hx of upper resp infections. He is becoming resistant to most of the anti biotics. My girlfriend said when he was on anti biotics he did not void outside the box. But he is on them now and he is still voiding outside and inside the box. His box is cleaned each day. The vet said he did not have an upper resp infection but the cat sneezes all the time, sometimes thick green snot comes out. He coughs, breaths loudly, and even sometimes mouth breaths. The vet kept him overnight and did not notice any of the complaints I had with his upper resp. I like the cat, he is a nice cat, but I will not live with a cat that is voiding outside his box. Oh and my girlfriend said he also likes to void on cords. I did notice on the cords across from the sofa he did void on them and inside the power strip which thankfully did not start a fire. Any help or ideas would be greatly appreciated since I fear it may come down to me or the cat, and no one will want a 12 y/o who voids outside the box.