I ended up having the Premier Cuvee dry yeast in my kit (2 packs). The ABV threashold is 18% which is 4% more than the liquid yeast. I actually called winexpert the maker of the kit to ask them my 2 questions. For the yeast they highly recommended using the dry yeast packs given and not the liquid yeast. They stated that they do extensive testing on the kit and to follow the instructions as described for best results. She said the liquid yeast I had might not break down the sugars the same way. I ended up using the dry yeast instead.
For the fortifying here is there response:
Thank you for your contact. Yes, you are correct - the yeast quits after it has converted all the sugars into alcohol and the gravity is constant at the reading as per the instructions at stabilizing. As long as there is a source of fermentable sugar and live yeast cells in the wine, nothing will prevent them from eventually refermenting the wine, unless there is also a sufficiently high alcohol content to help kill the yeast cells.
Although some people elect to fortify their Winexpert Port, we don't recommend it and therefore we don't recommend a particular brandy. Whatever brandy you use will have an impact on the flavour.
You should also be aware that commercially produced Port is not fortified with brandy. It is fortified with aqua ardiente, a 200 proof grape spirit. This raises the alcohol content without diluting the flavour. Commercial brandy is usually 80 proof. For every fifth of brandy you put in, you are actually putting in about one and a quarter cups of pure alcohol, and two cups of water. It won't drive the alcohol content as much as you might think.
Fortifying spirit is best added at fining/stabilisation. The alcohol in the brandy can coagulate the proteins in the wine, but if it is added at stabilisation, these proteins will settle out, and won't cloud the wine later.
Fortification can be calculated using the Pearson Square formula:
A (alcohol content
of fortifying spirit)
D (C-B) the difference is the fortifying spirit required
C (desired alcohol content
of fortified wine)
B (alcohol content of existing wine)
E (A-C) the difference is the part of wine to be fortified
It is necessary to know the percentage of alcohol of the spirit to be used for fortification and also in the wine being fortified.
Example: The fortifying spirit has 40% alcohol content, the base wine has 15%, and you want to increase it to 20%.
Subtract B (15) from C (20); the remainder D (5) are parts of spirit to be used in the mixture. Subtract C (20) from A (40); the remainder E (20) is parts of wine to be used. You will need 5 parts of spirit to 20 parts of wine to bring the mixture up to 20% alcohol by volume.