Also, should I repeat the flush with fresh water afterwards or allow it to remain in the lines?  Appreciate your help.

Since this will be a much higher concentration of chlorine than you would want to drink, please do empty and fill with fresh water. Flush that through the lines to purge the excess chlorine. Then you can drain and fill, even if only a few gallons, for regular use. I have dissolved some baking soda in water and used it in the tank when purging the chlorine to help eliminate the chlorine taste. However, if you have no intention of drinking that water, it can be used for flushing and likely, even showers. However, you can purge the lines when you get to your destination and connect up to the park water supply and leave the chlorinated water in the tank to help reduce the possibility of algae growth.

Depends on your bypass system.  Some have 2 valves others, like mine have 3.  Regardless of which system you have by turning the handles perpendicular to the pipe - that will be off or bypass.  On the 3 valves system the top and bottom valves will be turned perpendicular to flow to turn off or bypass.  The middle valve will be turned to the open or 'in line' or parallel with the pipe position - this is for winterization mode.  Do just the opposite when you wish to de-winterize.

I did not know about sanitizing the tank for the first 5 years of ownership and my wife and I use the FW tank for drinking a lot - fortunately we never got sick.  So finally on year 6 we sanitized but then had a problem with the taste of the water.  Took us a combination of 4 attempts to rid the tank of that nasty chlorine/bleach smell and taste.  Used a combination of 1 cup white vinegar, 1/2 cup baking soda and 1 cup of 100% lemon juice concentrate in 15 gallons water.  Run through all lines for a minute (skipped the toilet line) and let sit overnight.  Next day ran through all lines until we ran out of liquid - took about 20 minutes if I recall.

Using https://www.rvweb.net/how-much-bleach-to-sanitize-an-rv-water-tank/ - bleach to disinfect water tanks is not new to every RV, but how much bleach is needed to disinfect an RV water tank. We need to know the exact amount to kill pathogens and keep them at a safe level. In general, we will need one cup of bleach for every 50 gallons of water. Therefore, if your water tank has a capacity of 25 gallons, use ½ cup bleach. If your water tank can hold 12-13 gallons of water, use 1/4 cup.