I agree with C3H603 running 16 miles is a lot of miles for someone running 30-40 miles and also not not a seasoned runner, you could afford running very long runs if you were a lot faster making a come back from a set back even with 40 mi per week but even 16 mi way too much. My longest runs ever were 16 but I was training for a HM and was doing 60-65 miles per week. I was also running sub 16 5k. So I think you can run by time or mileage but 80 min should be plenty, try to run more often, I think 5-6 days of running will take you there. I would recommend 6 runs max, have a day off, that worked great for me.
Listen to your body when training hard and feeling tendon pains, take a day or two off, run ez is better to miss few days even a week than missing 6 months. Tendonitis is such horrible injury, but this usually happens when you’re pushing hard, doing increases in mileage and running speed work.
Example here if you’re training to improve your 5k start increasing your mileage slowly I think with 40-50 miles is plenty running and then you should focus on training to improve your times. That kind of mileage can easily be enough to run sub 17.
I was able to run even sub 16 with 45-50 mile weeks and 11-12 mi long runs. My fastest times were achieved while training for 1 mile race and was doing around 45 mi total, so my focus was on speed endurance and I did well, as I said many ways to train this might not work for you, but just giving you an idea. I had a friend that he would just do Mile repeats for endurance and boy he was a monster, but he was much older and ran his entire life since HS, he would run like 80-90 miles per week and was always few several sec per mi faster than me in the 5k He was in his early 50’s I was in my early mid 30’s, very different training with similar results.