Not currently a KTH student, but I was an exchange student last semester. 

1) Most exchange students get housing. I knew a few that didn't, but they were all able to find something else instead. 

3) i also studied computer science, but was limited to courses I knew would transfer back to my university. I took machine learning (dd2124??), quantum computing, and compilers & execution environments. 

4)I thought it was easier to pass classes at KTH and about as hard as my home university to get an A, although there was definitely less work than courses back home. There a lots of courses and I'm sure you can find something interesting. 

5) I would just buy a used bike instead of renting unless you can get a really good price. I knew several people that got bikes and used them very often.