How to appreciate my man?

I admit with both hands down, that I definitely lack in that area. He always says "I wish you'd appreciate me more." At least once a day, and I just don't understand how?
Like, I do the dishes, take care of the room (we live with other people), fold and hang laundry. Organize the mail. I compliment him daily and often during the day. I know there is more I could do, but I don't know what?!
I have an issue with my temper and getting easily irritated when I'm trying to discuss things that bug me, so it's quick to turn into an argument. He wants me nicer, and I can be sweet as a peach to him and his parents, but he also wants me to basically kiss his sisters ass until we move out. (which will be 3+ years) I can't help it that I don't like her, and fake liking someone just makes my temper worse because I can't vent, or say what's bugging me because it will just cause a fight.
Our relationship is on a tightrope because of how much we fight about his sister. I love him to death, but he won't let me vent about my issues to anyone else but him. But when I vent, he just tells me I need to be nice. I am nice! To those who deserve it.
And I'll fully admit, I have been pushy about him being "too nice." And I don't like it, because he lets her take advantage of him and on occasion, his wallet. And he gets almost flirty with women at work because he is too nice and let's them step over lines they shouldn't. I just want him to be able to put people, women especially, in their places and let them know what lines are being crossed and they need to back off.