This is for a small seasonal cabin renovation, it is supported on cinderblocks, no solid foundation, open crawl space underneath.
I have room in the cabin for a small bathroom, with toilet, sink, shower and tank water heater. 3 questions.

1. I have read that you cannot wet vent a water closet unless the WC is downstream of sink and shower. Does this mean if I dry vent the WC I can put it upstream of the sink and shower ??

2. The WC requires a 3 inch waste pipe. As I add in a lavatory sink and shower plus further downstream a kitchen sink will the 3" main waste pipe continue to be satisfactory for all 4 fixtures or do I need to increase to a 4" and at what point is the 4" required. The 2 sinks and shower will likely have an 1.5 trap and vent. I looked at the load factor tables and it was not clear, must be reading it wrong.

3. I have a small space for the WC. People tell me it is code to have 30 inches wide for the toilet, but I can find no reference in the Canadian or Manitoba Plumbing code regarding that and the National Building code only mentions 30" is suggested but not required. The water heater will be beside the WC sharing about a 44 inch space. The water heater is 18 inches which leaves about 26 inches for the WC. But as the water heater is round it bends away from the WC thereby creating more space.

Can anyone clarify the 3 above questions.
thanks your input