2009 silverado 5.3 rough idle misfire 7

My truck sat for almost a year because i ran over something and it busted my
gas tank and i had another car so i didn't need it. my husband took the tank
off and then stopped working on it and then he passed away from a car
accident which put me in need of the truck. I put the tank on it wouldn't start
so i replaced the pump and it didn't get good fuel on the rail and check
engine light was on. It said that i needed fuel module so i changed that. It
worked and I took it and go a tune up, it ran fine for about a month.
Now its started running awful. When its idling its missing when i shift it into
drive and hit the gas its giving a funny kind of knock but only when gassing it.
It got so bad that i couldn't drive it in D I had to put in it manual and drive it
with rpm pegged a 2000. I checked the codes and it was giving me misfire on
7, and 2 codes for cats. It felt like it wasn't taking gas right so i got a bottle of
injector cleaner and it ran much better.  As the tank got closer to empty it
began with the funny knock again. It not got as bad as it was before but its on
its way.
Yesterday i checked the codes again to see if anything had changed and it
was now giving me misfire on 7, mass air flow code, one about emission
small leak, and the cat codes are gone. Does anyone know what could be
causing this? I dont have much money right now and really cant afford to
take it to dealership. Thanks