I doubt that you will need to install chains in April. Weather should be breaking into spring.
Your speed is alittle slower then we traveled the Alaska Highway.
You need to keep an eye your fuel gauge. Fill up more often. Fuel is available however stations are farther apart. Your 300 mile range should handle it. 10 gallons as precaution will do.
Your good condition tires will do the job on most roads. Some of the shale gravel roads in the Yukon can be rough on tires. You might think about carrying an un-mounted spare, however it may not you do any good when there is no tire service location to mount it. There are tire stores along the route in most larger communities.
Not sure where you are going to use sail boat. Is it worth taking is your call.
It is a great trip!
