Good luck. Any time you get close to 83% you are moving. Let me know how it goes. I had similar experience between the roads and track, always faster on the track age graded.
A triathlon friend of mine was a top 10 finisher at World 1/2 Iron Man last year. Very good 50+ athlete. He has been fried psychologically for months now. Hey it takes a lot of physical and mental effort to keep this going. Unfortunately, as you get older you have to do that many more things correctly to keep it going.
As I mentioned I had the self imposed injury break during the winter, so I have had my down time. Besides, the better racing here is spring and summer. My activity level is higher, this week should log: 1:50 spin bike, 1:20 core/weights, 6.5 miles walking and 24 miles running. At the moment I am trying to increase the total volume.
Several of us on the 50 Year and Over LR Thread have made commitments for a fast mile time this season. To accomplish this I need to increase the volume, because in the end I am a distance runner trying o be a miler. Therefore lately just trying to get a balance. Last season I just focused on quality running and did not spend any time on core/weights. Generally the thought is emphasizing things that have worked in the past. A staple for me has always been a long run once a week. Getting back to that. Last week I ran 9 miles in the foothills with 1,000' plus of elevation gain. This week moving up to 10 miles with probably at least additional 100' in elevation.