I had some major issues with mildew in my basement a couple of years ago. My contractor advised me to buy a cheap pressure sprayer from the lawn and garden department of Home Depot(about 2-3 gallon with a pump handle to build up pressure with a slim nozzle sprayer) I filled it with a solution of about 3/4 bleach and 1/4 water. Then I sprayed it on the affected areas 2 days in a row.
If you do this, you MUST wear gloves and a mask and cover your hair and skin. Also, do not plan to use the bathroom for at least 8 hours after you spray because bleach is a toxic solution.
After the mildew was gone and the bleach was dry, I just painted with regular paint and I have not had a problem since. However, I also fixed the source of the moisture that cause the mildew in the first place. I think there is mildew resistant paint you can buy but it is expensive. Since it is a small area and your probably only need a gallon then it might be worth it for you.
I have no advice on the toilet. I tried to fix a running toilet and it turned into a 3-strikes (i.e., I tried 3 different times...) and I was out big fail. I had to get the contractor to fix it for me.