https://baseballsavant.mlb.com/ has great tools if you want to dive deeper into baseball metrics.
They have everything from spin rates, pitch movements, pitch usage, live tracking exit velocities, launch angles, barrel %, hotspots, etc
1. Aside from the ones above: wOBA, line drive rates, whiff rates, walk rates, contact metrics, sprint speeds
2. Are we talking about fantasy baseball tools?
3. I try to dive deeper into players, metrics and stats only tell part of the story. A lot of the game is mentally driven. It's all a lotto, but certain teams have an edge in player development which increases a prospect's chance to succeed. Scouting tools is important and that's what most people do, but when you invest in the players themselves and not their stats its easier to root for guys that go through growing pains. None of the players drafted are finished products, there's really no telling how far they'll go. All these projection systems and models are not perfect, that's why there are breakouts every year where players way exceed expectations or fail to meet their hype. Injuries also play a huge factor in a player's career projections, and it's next to impossible to tell if a 18-21 year old kid will stay healthy for the next 10 years.