Choosing Appropriate Training Paces

When I use two different performances I get very different outcomes on the pace charts. In a recent, solo and very smoky 5K at 5000ft I ran 17:06. I think it is fair to choose a mid 16 off the pace chart. This gives me a projected 400m/800m pace of 62/2:12 although I am fit enough to go <53/<2:03. I've always been more on the speedy end of the spectrum. If I use those performances the middle paces (10K to 3K) are too much to handle right now. I've read it suggested to use two pace charts for both performances, but where is the reasonable cut off for each chart? My Goal race is the US Paralympic Trials June 2021 for 1500m and 5K so there's a lot of time and I don't want to mess up appropriate training paces. Thanks!