You sound as though you have your compass set in a direction worth working for. You also sound as though that your intentions are well matched with reasonable expectations and assumptions.
For what it's worth, I'd like to give you some advice that is based on my observations of those that have made it in professional baseball.
Consider this as a profession
Like any professional - lawyer, physician, certified public accountant, and so forth, it take years of study and dedication to the profession and the commitment to narrow one's focus of that profession as one matures.
Your mentors as coaches
Planning for a career in professional baseball is the cruelest thing that a young man can commit himself to. The expectations of performance by those with little or not experience coaching the development and progression in this sport, will constantly nag your as get older. Your development will be of little concern while with these coaches, only your ability to fit into the self imposed image of these coaches as they are viewed by their contemporaries. You will find exceptions to those statements - but those exceptions will be rare are far between. So frustration with when and where you fit into the game plan can, and will be a test to your patience. However, improvement will be expected and that expectation will increase as your get older.
Unlike other professions that have formal schools, formal accreditation and certification, professional baseball has absolutely none. There are not degrees conferred, no diplomas, not even two-bits for a cup of Joe. So the benchmark by which other professionals - lawyers, CPA's, engineers, and so forth, can be judged, does not exist for professional ball players. You must educate yourself, set forth your own level of education and proficiency, be judged by those whose qualifications vary widely - yet stick to you like glue, as your negotiate the waters of appraisal. You will sometimes find family and close relative that will find you former professionals that will offer coaching - for a price. Along with that finding will be the adult assumptions of this former pro turned coach, being there to introduce you to "who they know" in addition to showing you what they know. All adults live in that world of "who you know", (even me) and you'll become accustomed to that way of living soon enough. It's a big part of the game/business.
When it clicks
Regardless of what I narrated above, many have made it. They've made it in spite of everything that worked against them and contrary to the odds. They made it by setting priorities, hard priorities that meant sacrifices, upon sacrifices. They were right there along side the buddies that trained to be professional hockey players - up at 4:30am to make it for ice time, then an hour and a half of ice time, shower and in the classroom between 7:45am and 8am. Only for the ball player, his training routes were tailored to baseball. Strick nutrition tables, time management, deliberate academic commitments, studying the rules of the game, personal conditioning and strength tailored to his age, his physical maturity, and stamina.
One of these days, regardless of who says what, you know you've got it. Things start to click! Your confidence is as much a part of you as your own name. You're not the best in town, but everyone knows your in town when you take the field. You've made it! Now it's just a matter of time (be patient) for the rest of the world to catch up to you. Catch up to you!
We're here for you
You'll find an impressive rank of coaches, players and others who will be right there with you, every step of the way. And although this medium is limited, there is so much that you can learn and apply from here. Add to that - everyone expects nothing in return - but, your improvement and enjoyment of this game.
I've said this many times that pitching is not for everyone. If it was, it'd be easy. It takes a special person to understand his limitations, his place in the pecking order of things, and his understanding that this life is not fair.
ONE - It take guts to want this.
TWO - It takes guts to work through that want.
THREE -It takes guts to wait your turn.
Got any questions? Refer to number ONE.