If this is your tennis season, and you want to do well now, adding in a lot of new training is likely to to adversely affect you in match play.
The time to work on a balanced program is well before your season starts, or after it finishes.
Here is a site that will give you a balanced look at off court training: Sports Fitness Advisor Tennis Training
http://www.sport-fitness-advisor.com/tennis-training.html
"The Periodization of Strength
To promote long term training improvements and
avoid over training, an overall training program can be split into specific periods, each with their own objectives and set of training parameters. This concept is called
periodization and it is the most effective approach to planning strength training programs for sport.
The overall training program (usually taken as one year long) can be split into set periods and usually consist of the:
•Preparation Period (Pre-season)
•Competition Period (In-season)
•Transition Period (Off / closed-season)
By co-ordinating the different elements of a strength training program with the phases of a typical season, the athlete can reach a peak for the start of the competitive season and most important parts of year."
So again, it sounds to me that you are already spending so much time on court, that adding in more training right now will just lead to over fatigue and burn out.
Tennis is a game of skill, and this may be the best time to take advantage of team mates to keep working on your rallying, vollying, returning and serving work after formal practice.
Work on coming out of a split step on every shot.
Work on recovering as quickly as possible after each shot wo that you are ready for the next one.
After your high school tennis season is over, you can intensify the weight training programs from the above site.
You may also want to add in:
HIIT - High Intensity Interval Training
http://www.intervaltraining.net/hiit.html
USTA agility drills done as a form of HIIT
http://assets.usta.com/assets/1/USTA_Import/USTA/dps/doc_437_269.pdf
If you want more advanced work out programs coordinating weight training, HIIT and agility drills, consider getting
Power Tennis Training [Paperback]
Donald A. Chu (Author)
http://www.amazon.com/Power-Tennis-Training-Donald-Chu/dp/087322616X
If you would like a deeper understanding of how to train, consider getting
Tennis Training: Enhancing On-court Performance [Paperback]
Mark Kovacs PhD (Author), W. Britt Chandler MS (Author), T. Jeff Chandler EdD (Author)
http://www.amazon.com/Tennis-Training-Enhancing-On-court-Performance/dp/0972275975/ref=pd_sim_b_4
Are you playing tournaments this summer like your future college competition is?
While I commend your desire to improve and potentially play college tennis, realize you are at a disadvantage compared to those also willing to work hard but have the advantage of great coaches for guidance.
But there is every reason to believe that tennis can be a great enjoyment for your whole life, even without killing yourself or making a college team.
There almost always is plenty of local competition to give you a good, enjoyable match and a great work out from tennis.