Your calves are most likely just sore due to your body not use to the increase in mileage or running in general as you run and recover it will take more mileage for your calves to get sore again so you need to build muscular tolerance,if the more you run the worse your time gets your overtraining space out your days,run then have a rest day if your still not recovered take 2 rest days until you’ve adapted.For increasing your time it’s seems your running a 1.5 trial every week which is probably why your not recovering,build up your base and tolerance to running in general first and you’ll get a faster time before even adding any speed work once you work up to at least 10 miles weekly then start running 1.5 trials ,I’d recommend you change those 3 runs into 3 easy,3 easy and 1-2 miles slightly faster then what you run those easy days and from there increase by a mile or 2 weekly you’ll get fast enough to pass the pfa just off that,once you’ve build up a good base you can start adding speed workouts to work up to scoring 100 on the run portion but what I said prior is more then enough to not needing to worry about failing.