I mix it post fermentation, though the mead is pretty good on it's own. Looking over the recipe it's almost exactly what I make. I add the vanilla and cinnamon to the secondary for around a month or two, though I found a "forgotten" batch that had it in for 8 months, didn't effect the flavor very much but it made a huge difference in clarity. I always say you should stop it when you feel it's reach where you want it. remember though if you are going to add honey to sweeten it back up post fermentation, make sure to add some potassium sorbet to stop the fermentation from kicking back off. I ended up with a very dry, very alcoholic (24%) very not good mead by accident that way. As for yeast I'd use a white wine yeast from red star with an alcohol tolerance around 12-15% (I normally end up around 12-13%)
Hope this helps.