He is actually OK when it is just him and me together, but when my wife is around (most of the time of course) he is a pain.
We have the same. My little one s a lovely, well-behaved kiddie when we are together. We went to a pub down in Kent, she drunk her OJ, ate peanuts, talked to the dog that was there, was quiet and playful at the same time. When my wife is around, the kid turns evil. She whines, screams, gets moody, becomes a royal pain.
When I take care of feeding, whatever she gets she eats, broccoli, carrots, bangers and mash, pasta, anything goes. Mum feeding – don't want this, don't want that.
Solution – spend more time with your kid, take him out and about, talk to him, teach him stuff Mummy never will (ok, buying porn and drinking ale should possibly wait a bit). Be a hero. Even if the little devil doesn't appreciate it now, he will later.
Good luck (and ensure no more kids), only 21 years till they both move out.