Just because you didn't retain your speed in years past doesn't mean you didn't retain it this year. Your speed might improve a bit on the road to May but the gap from 24 to 22 is a lot bigger then 26 to 24.
Also, a 100m sprint is no indication of an 800m race, which is primarily an endurance one. Assuming the distance was right (which might be quite an assumption, I don't know)
Best case scenario: with a bad start, tiredness, 95% effort, etc the 12.1 was worth 11.5 all out. The 11.5 all out is worth 22.5 all out because you lose time at the start. The 22.5 will be improved by about a second by May based on your previous history of improving a lot during speed training. You said you have been up to 80-85 miles per week and are doing 50-60 miles per week now with tempos etc-that suggests at least good endurance. With no knowledge of longer race times it is hard to predict anything, but I would say your times in May would project out to 11.2, 21.5, 46.5,---1:46
Worst case scenario: 12.1 is all you are capable of and you will run no faster then that by May. Your endurance is poor despite reported mileage and your distance races are lackluster. Worst case-12.1,24.5, 54,---2:02
avg of worst and best=1:54...1:52-1:56 is certainly possible, 1:50-1:52 or 1:56-1:58 would not surprise me much either. However, I doubt you will be under 1:48 or over 2:00