2001 S60 P0420 with P0455 issues

[Lunawolf]

I have been trying to trouble shoot this issue for a bit. Have been keeping tabs on the codes as they come up. Have noticed that cata is showing good, but after the Evap issues start pending the Cata P0420 will also start to come up pending and both will post around the same time when they do fully post. Have noticed that loose gas cap message will come up at times then the pending P0455 will show up. Have noticed in past quick post codes that come and go with misfires, ignition coil and electric Fuel level malfunction. But have not seen these come up often. I did find one issues that has been bothering me for a bit today, pulling out the backseats as prior owner stated they had replaced the fuel pump recently before I bought it and noticed that the sending unit has fuel around it. Being there is some type of leak, maybe a faulty sending unit gasket, could this be starting to cause all these issues with cata checking good then evap setting off the cata code for possible vacuum leak due to loss of good pressure in the gas tank? Also noted some really small pitting in the resonator, but would that be to far down the line to cause issues? Former owner did say something about a j-hose probably needing replacement, but question with the fact that about the leak in sending unit if that may have been the possible issues? Any suggestions would be good. Also the car has large amount of miles over 227k, but engine is in really good shape with basically no rust outside of a little on drivers door.