Hi again,
Sorry I missed your previous post. Lake Toya can be accessed from Toya station. There are buses from there that take you to the lake in 25min.
For Sapporo:
I think taking a day to explore the city is great, walk around Odori Park and Sapporo tower, visit Sapporo Beer museum and try jingisukan (Hokkaido meet dish named after Genghis Khan) for dinner. Moerenuma Park is a very pleasant park to walk around as well but a bit far from Sapporo. If you are interested in History, then I recommend including the governor house as well (its free).
Sapporo is also great for night life, its great to just walk into a pub and talk with the locals or fellow travellers.
Otaru also makes for a great day trip from Sapporo. You can have some of the best Sashi there. I think you already had this included.
Note that Sapporo station is not in the centre of the city, its still a nice area. Just something to keep in mind.
These are sort of random thoughts but the first that come to mind with Sapporo. Hope you find them useful.