There is no set number of d and u tokens. You convert your sxs tokens to d and/or u tokens at whatever ratio you choose. It is 1 sxs for 1 d or 1 u token. If you had 100 sxs tokens you could turn that to 100 d or 100 u tokens or a mix of d and u such as 30 u and 70 d.
This is extremely unlikely as not everyone who will invest in the project will want to use the platform.
The price is 1 eth = 2000 tokens plus any bonus. For the pre-sale, that was 33%. During the first week of the main sale that is 11% and no bonus after the first week.