You must not be aware of the research on Non-24[1] (or "Non-24-hour sleep–wake disorder") which OP seems to have (though perhaps they also aren't aware this is a thing).

Not saying non-24 is good for you, but for people unable to follow a 24-hour schedule, free-running sleep (which is what OP is doing) is vastly better than constantly pushing through sleep deprivation, when one's schedule allows for it.

Speaking as someone with non-24 myself (which is much more severe in the winter)

edit: after reading more closely, it appears OP has entrained to a 28-hour day rather than doing free-running sleep; 28-hour days are convenient in that the week gets sliced into 6 days and allows for a consistent weekly schedule. However, I suspect OP actually naturally gravitates towards a shorter day like 26 or 27 hours based on their napping patterns. I also wonder if they might even have more success with 24-hour days and regular exercise, as from their description it almost seems like the daily exercise practice which they started after the 28-hour day might be regulating their circadian rhythm to be closer to a natural day.

[1]: https://en.wikipedia.org/wiki/Non-24-hour_sleep%E2%80%93wake...