To your first point, I think it depends greatly on where you look. If you zoom in on Burnet or Boerne I'm guessing you might find more miles of trail open to ebikes. Sure, if you focus on Austin you won't see much because the trail networks are primarily located in city/county parks.
I don't ride as much as you, but mine would be closer to a 50/50 split between public and private trails. I typically do a mid-week ride in town on public trails (Brushy, Ninja, Walnut, Lakeway) and a weekend ride on private trails (Spider, RPR, Flat Creek, Flat Rock, etc.).
My riding these days is less about miles and more about smiles. Riding downhill makes me happy, so I'd rather do more of that. That's why I'm at Spider just about every other weekend. At places without a lift, an ebike would give me the opportunity to double the number of laps on any given day. Again, I don't have one. But I see their place and I am definitely not ruling out the possibility of owning one in the future. I resisted dropper posts for a long time. Hopefully, I've learned from that experience...