Re: "I'm too tired"
One of mine went through this phase. When he was too tired was brought up I immediately took away what he wanted and said "oh, ok none of this then since your too tired." and I'd tell him to go take a nap. Sometimes there would be a tantrum but I'd act oblivious to it. Eventually... 15 mins later or so he'd come sauntering out of his room saying he was better but wouldn't be allowed to do anything else before the first task was finished.
Now with the food thing I'd tell him he can eat or nap. If he was too tired to clean better nap, eat then clean and you have no other choices. I just stayed calm and acted very serious like oh you must really be tired, lets sleep! That always bugged him. lol I just wouldn't let him get away with anything. He eventually got tired of it and wasn't getting any help or attention for it so he stopped. Honestly, to me it sounds like your doing what I did. It does go away... I promise!