Clarification of Manitoba/Canadian plumbing codes

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
jeff

Often times newbies want to do the least with the waste and vents, considering many ways of wet venting without the know how and rules. You can always vent the fixtures in the normal fashion, the cost is almost the same, and tends to be easier to come up with a workable layout.

Normally a 4" line is need after the forth toilet enters the line.

A gas water heater can't be in a bathroom or bedroom.
I believe you can get by with an electric heater.
The 30" is mainly about room for your arms.

that's why I am on the forum asking questions terry. just wanting an understanding of the codes that are sometimes not quite clear to a "newbie". it matters not which way is easier or least expensive, I want solid ground for my construction so I don't get flack from the building inspectors form the small town jurisdiction.

If the toilet drains down toward the lav, you can run the lav and vent with 2" and that would wet vent it if the take off is within six feet of the toilet.
A tub or shower can also be used.

A kitchen sink or washer can't be used as a wet vent.

jus tto add to what Terry has said.... the went vent for the toilet, according to our code, does not need to be within 6 feet. The measurement is 1meter vertical and 4 meters horizontal. so your toilet drop leg can be up to 1 meter and then 4 meter horizontal before vent needed. you can wet vent the whole bathroom group by having the lav wet vent the toilet through a 2" wet vent and the shower, as long as it is not more than 1.5m from the 2" wet vent, can tie into it without needing a separate vent. you still need to meet all other requirements of venting fixtures including the proper distances change of direction etc.
if you're not 100% confident to install that set-up then it may be easier for you to vent each fixture or hire a professional.