I use an app called Strava, which I start up when I begin a ride. It auto-pauses when I stop and resumes when I start moving again - I put a link in the description which notes the distance and I think avg. speed. I can see more details on overall and segment speed - I think you can too if you sign-in with an account.

It looks like my avg speed on this ride was 10.2 mph (lots of uphill). My top speed was 31.6 mph.

I'm ok sharing the trail. There have been horses out here at other times. The western portion of the area isn't as heavily used as the trails aren't marked or maintained as well and they're further away from the parking area.

Not as many as earlier in the summer, but I saw 3 in one day earlier this week.