In your limited time to get in shape, it will be quite difficult to go sub 1:50. I think most good 800m runners will tell you that a long buildup is needed to reach the goal you have in mind.
Here is my take on your requirements to go sub 1:50. First, you will need 400m speed of about 50.4 or faster to go sub 1:50. You need speed cushion and then speed-endurance. It is important to do quality workouts, yet do endurance running too. If you can run some long intervals like 600s at 4-6 seconds over your current 800m race pace, I think you can speed up the process of getting the needed speed-endurance. So, for example, let's say your current 800m time is 1:56. A good workout might be 4 x 600m at 1:31-1:33. If in doubt, jog farther for recovery between reps so that you can be assured of running the next rep at the required speed. As a general rule, jog nearly twice as far as the rep and then run another. I'd rather you run 4 reps of 1:32 with a 6 minute jog than 3 reps with a 5:00 rest but slower times when you are working on your conditioning. Later in the spring, you can reduce the recovery once you hit the times that are close to your goal pace. If you are hitting 4 x 1:26-27 for your 600s with a 1000 jog in 6:00, then you can reduce your recovery jogs and that will aid your speed-endurance. I think you might find it very helpful to run a couple fast 200s with a 400 jog after each longer rep session. You can run the 200s at about your 400m pace plus 2-3 seconds, divided by 2. So, if you can run 52 seconds for an open 400m run now, then add 2-3 seconds and divide by two for a 200m rep time of 27-27.5. By time April rolls around, I think you can be hitting your 600s in the mid 1:20s and your 200s in 26.
In the late spring, you and your coach will have to work on honing your speed for the key races, so workouts like 3 x 400m or 3 x 300m or 3 x 200m at close to full effort will be important. It won't do you any good, though to hone your speed while neglecting your speed endurance and aerobic endurance, so be mindful of that.
Take it one week at a time. Focus on what you can do this week to improve your fitness, take care of your health, prevent injuries, nutrition, etc. Also, consider doing mential imagery training in a systematic way, not just thinking about it. Seeing it happen in your mind daily, while in a relaxed state and practicing making mental race moves will provide you with confidence for racing relaxed and will full awareness. You know how important it is to cover moves while staying relaxed. Mental work can be valuable in this regard, if practiced regularly. Appreciate your mind, it is your secret weapon.