Mold is a type of fungi and can be found almost everywhere. Mold develops in the places that are humid and dark. One of the most affected places is the one where your food is kept. In order to get rid of the mold you need to dry the affected area for a longer period of time. Washing, cleaning...
It is true, seed tannins can create bitterness to the wine. You can use Malic Acid along with your tannins to reduce the seed tannins. You can also try using 100% oak barrel for all your ferments, or at least for the ferment of the red grapes. This will help the wine not to create too many tannins.