1) People can be very particular about countertops, so I would not make that change before putting it on the market unless it is in poor condition. Instead, you can give them an allowance if it becomes a sticking point. They might want to redo the whole kitchen.
2) Yes, paint is the cheapest way to upgrade the look of a house.
3) If it is unsafe, I would fix it. If not, let the new owner decide.
4) Where is the current laundry? If there is not one or it's stuck in the kitchen/basement, this might pay off.
5) Yes. Refinish the floors.
6) Luxury vinyl tile might be a good alternative.
So, my order would be:
2, 5, 6
distantly followed by 3, 4, 1