You have to realize that everyone's injuries are different even though many of us have very similar symptoms.
I think my main mistake with that snowmobiling trip was that I went from like 10-20% activity level (Only activity I did were the 20-30 min easy walks every day) to 90-100% within one day.
Another thing to keep in mind that some people might have actual injuries to other organs in the head, not just the brain. For example I was diagnosed with a fistula in my inner ear recently, and that would explain why every time I exerted myself I felt way worse for a while (fistula reopening and then slowly healing again).

I understand what you're going through right now, trying to find all the answers, I think all of us on here were in your shoes at the beginning.

The simple truth is that there isn't a set of rules for recovering from PCS, everyone's situation is different. I have friends that suffered head injuries that were way way worse than what I had and they recovered within 1-2 months.

One advice I can give you is start very easy exercises, like walking for 15 mins and see how you feel the next day. Do that for a week, and if you feel fine move to 20-25 mins walking.
Then try a stationary bike with a heart rate monitor. Try to keep your heart rate elevated for 5 mins at first, again see how it feels and slowly increase after one week.
I started with like 80 bpm for 5 mins for a week and went up from there very carefully.

There is research from the University of Buffalo (http://concussion.buffalo.edu/) that seems to show very positive results from careful cardio exercises (usually over a span of 3-4 months).