LB training to be a SS

As far as increasing speed, I am assuming you are around 18-19 years of age (with high metabolism) and at a pretty low bodyfat %, (probably around 10-12%). Since you probably don't have much bodyfat to lose, the key here is to increase your "Relative Strength", or your level of strength compared to your bodyweight. Think of this as keeping the weight of your car (your body) the same, but increasing the size of your motor (increasing strength).

What is your current strength level? Unfortunately, most young athletes are weak in the hams, glutes and low back (posterior chain). Increasing strength in the posterior chain will definitely help in getting faster as long you don't gain much bodyfat. Exercises like Good Mornings, Reverse Hypers, Romanian and Stiff leg Deads, Snatch grip deads, sumo deads, glute ham raises, box squats, etc. will develop alot of strength in the posterior chain. As an athlete, these kind of lifts should make up the core of your workouts. If you are going to continue a 3 day split, you will be better off training the entire body 3 days a week than by using the routine you are using now. Right now you are using more of a bodybuilder's split than that of a football player. Just make sure that you use a lower volume (sets x reps ) than you would if you were training bodyparts twice a week. Also, make sure to cycle your lifts, reps, intensities every 3-4 weeks so that your body does not adapt to the same routine over and over again. You must keep the body guessing.

I know I gave you some exercises for the Post. chain, but you also need to be sure that you are not "wasting time" in the gym by doing lifts that won't help much with football. If you MUST do curls, which I don't think are worth much in terms of football, then do things like forearm curls or zottman curls. Sitting around doing 5 sets of incline curls or concentration curls, etc. will just waste your time and negatively affect much needed muscle/strength gains. Instead of doing isolation lifts, concentrate on things like pull-ups, chin ups, dips, overhead presses and of course the olympic lifts. All of these lifts will build bigger arms, and more importantly, will be transfer on to the playing field. The only muscle I would even consider isolating would be the Triceps, because they have such an important effect on the bench press and over head lifts. Pull ups and rows will build powerful lats which will also important. And last but not least, one of the most neglected bodyparts, but one of the most important is the ABS. Train your ABS like its going out of style. Hanging Leg Raises, Weight resistance sit ups, ect.

Another thing, Plyometrics, depending on the intensity, can be extremely taxing on your body and if done too much at too high an intensity, they can affect your strength gains greatly (in a negative way). I would drop the plyos for now and concentrate on max strength. As the season approaches, pick up more sport specific training (such as the plyos) and increase the intensity of your oly lifts (clean, snatch). Just make sure that in the meantime, you ARE doing some sort skill training that deals with sprint technique, and your position skills at least 2x per week.

If I can make a suggestion, you should research the subject of strength and cond. with reckless abandon. There is alot of info out there that can benefit you as a strength athlete. The more you know, the better you will be able to find what type of training benefits YOU as all athletes are different in certain aspects.

Hope this helps and best of luck to you, athlete.