You say tendonitis who gave you that diagnosis? Doctor or PT?
If you are weight training everyday, you probably need to cut that out. your body needs time to recover so it can heal and grow. What are your splits?
Pull ups, cleans, back squats (without a safety bar) and any elbow heavy work needs to be cut out now. Find a good PT or Good Sports Trainer and talk to them. If money is an issue find one who will talk to you for free. They are out there.
Contact Cressey or TreadAthletics and get as much information as you can.
What specific elbow exercises have you been doing?
I don’t think you will be well advised to completely stop throwing 2 weeks before the season starts. Very light throwing while stopping the elbow workouts may be better but you need to find someone local to talk to and get your pain under control as soon as possible.
I am not trying to alarm you but I want you to talk to someone who can give you some idea of what is going on. That can’t happen over the internet.
It sounds like you may have some talent, don’t take it for granted. Take care of your arm.