If the coach is keeping you on the team, use the practices and games to work as hard as you can to improve, and study the game. And for sure, try to have a conversation with him, outside of practice, to ask where he thinks you need to improve. Can you talk to assistant coaches? Do you stay after practice to hit in the cages, throw, field? Injuries happen. Be ready.
You don't say whether you do workouts, lessons, practice outside of the school team - but, right or wrong, that's kind of expected at most high schools. Do you play in the summer at all (you said "not travel")?
I understand that it's mystifying sometimes why a coach plays certain players and not others. My son was confused about a lot of things when he was in HS. Later he was an assistant coach for one year. He said now he understood and agreed with all the coach's decisions back then.
Generally speaking, coaches are trying to win, and they play the players they think will help them - but it's not always obvious what that means. Maybe some are better contact hitters? Maybe they hit the ball harder than you do? Coaches always want pitchers - but probably he knows more about what kind of pitching succeeds at your HS varsity level.
"Playing in college" can mean many things. Do you mean that you want to be on a team, even if you never play? There are many colleges that take as many as 50+ players (i.e. paying students) - these are D2, D3, NAIA, etc. Only nine play at anyone time, though. It still could be a good experience, if you like being around baseball.