Yes, any extra bacteria will simply die off as it has no food. This won't hurt the tank but will mean that if you do add extra fish later on there will be a mini cycle. This won't be as bad as an initial cycle though as all of the bacteria are present in the tank, they just have to increase in numbers again. So if you add extra fish later make sure to test the water and do any water changes that you require to keep all of the level low.
As for how much ammonia to add. Unfortunatly you are goning to have to figure that out by trial and error the first time. Each tank is slightly different in how much water is actually in there and things like gravel are going to make a difference as well (volumn of course).
So the first time I suggest start very slowly, add a drop, do a test, ect... This should give you a good idea of how much will be needed to top off the tank later. This is of course why the test kits are so important. My ammonia test kit is good enough for 75 trials and I am sure there are others out there the same. I would suggest writing down your results and keeping them in case you want to fishless cycle again. That way you will have some sort of reference point. It won't take very much ammonia to do this so buy the smallest bottle of pure ammonia that you can find.
