Has anyone got any tips before I commit murder 
I have 3 cats, they were DPs before we got together, I have 2 dogs if that's relevant.
The cats are house cats and have never been out, DP refuses to let them out and gets angry if I mention it incase they get killed. Two are roughly 5 years old and the final one is about 2.
Problem is they are always causing trouble. The main issue is the stealing, they will steal any food available. They steal ANYTHING...bread, cake, leftovers. Basically anything, packets are no problem they just rip those open and eat what's inside. All food is now under house arrest and we have to hide food in places the cats can't get too. I have no idea why they do this as they are fed more than enough and all 3 are on the fatter side.
They also will greed while you eat and then run to the sink to lick the plates 
I have spent months putting them on the floor but they don't learn and get straight back on the counters repeatedly and its driving me nuts!
Can you train cats or am I fighting a losing battle?
I am desperate to just let them outside but I don't think he will ever forgive me if something happens to them.