Let's see if I can answer a few of your questions.

1.  A vinegar rinse is not quite the same as using a clarifying shampoo.  However, if you use the rinse regularly, you may not require the clarifying shampoo.  You can use the vinegar rinse as often as you want.  Growing up, my mother did vinegar rinses on my sister and herself every time they shampoo'd.  With my blonde hair, she did a lemon juice rinse instead.  Today, I prefer the vinegar over the lemon rinse.  The lemon rinses can get sticky.  If you use products that are more prone to buildup - such as containing either proteins or -cones, you might want to use the rinse more frequently than if you use lighter products.

2.  The less you handle your hair, the less you stress it and potentially damage it.  The handling of your hair during shampooing can be stressful.  Also, the more you shampoo, the more you remove the natural oils which causes the scalp to keep trying to replace them, which causes your hair to be more oily/greasy.    Once your head is "conditioned" to less frequent shampooing, your scalp will reduce the amount of oils produced.  Daily washing usually is not necessary once you have adapted to less frequent washing.  The length of time between shampoos is an individual thing.  I can easily go 7 or 8 days between shampoos during the winter and 6 - 7 during the summer.  I do rinse my hair after "working out" and if I sweat alot, I might use a thin conditioner on my hair which will help cleanse it without using a shampoo.  You might try the conditioner trick after some of your workouts and see if that might work for you.

This routine is most certainly less harsh than daily shampooing.  Good for you!

I'm not sure what the answer should be on leaving the hair dry or water rinse it.  The water will help to add moisture to the hair and will rinse some contaminants away, so there is a benefit to water rinses.  But, if your hair looks fine without the water rinses, then I'd say do what is comfortable for you.  You might find some days you don't want to deal with wet hair, so put it in the shower cap.  When wet hair is not an issue, go ahead and water rinse it.