I still don't know whats wrong with my car?

I HAVE A 2002 NISSAN SENTRA SE-R SPEC V 2.5. THAT I JUST BOUGHT OF A PRIVATE OWNER, DURING A NIGHT HERE IN ARIZONA IT DROPPED TO 13 DEGREES WHICH ISNT NORMAL FOR THE STATE. THE NEXT MORNING I GOT IN A LEFT TO WORK I NOTICED THE CAR WAS RUNNING ROUGH AND WEAK BY THAT TIME MY UPPER RADIATOR HOSE BUSTED AND MY SERPENTINE BELF CAME OFF (IT DIDNT BREAK) SO I DROVE IT BACK HOME LET IT COOL. LATER THAT DAY I REPLACED THE HOSE AND THE BELT, AND TOOK IT FOR A DRIVE AROUND THE BLOCK, I NOTICED THAT THE ENGINE TEMP WAS RISING WHICH SEEMED ABNORMAL TO ME SO IN FEAR OF OVER HEATING I TOOK IT HOME, AFTER SOME RESEARCH I CHANGED THE THERMOSTAT THINKING THAT WAS THE REASON THE TEMP WAS RISING. AFTER 24HRS FROM REPLACING THE THERMOSTAT I DECIDED IT WAS TIME TO START HER UP AND TAKE IT FOR ANOTHER DRIVE. BUT WHEN I WENT TO START IT I CRANKED BUT DIDNT START I CHECKED THE FUSES TESTED THE BATTERY, TESTED THE FUEL PUMP, SPRAYED STARTER FLUID THAT DIDNT WORK, REPLACED THE CRANKSHAFT POSITIONING SENSOR WHICH WAS NEEDING TO BE REPLACED DUE TO CHECK ENGINE LIGHT IM RUNNIG OUT OF IDEAS ON WHAT IT MIGHT BE CAN ANY ONE HELP???