I am not quite 60 but in July Lord willing. I am retired so I ride many miles but I must say COVID got me out more just because nothing else I had to do or could really go. Myself I ride early in the morning year around and although I like heat what you did in Tulsa was pretty hard. The combination of heat and humidity but that ride at the limit for most folks. For myself I find that getting older and not the pandemic I lose the ability to bring up really high power on the bike. I have endurance and can go on and on but when it comes to a huge difficult climb or other situation, age will take its toll. I notice on Grand Fundo's when I ride with others and I usually can ride strong I just don't have the energy to keep at it as I did even 10 years ago. However what I do notice is I don't take breaks or even had to take a break. I can pass up aid stations and rest stops and just keep on at a slower pace but many times end up finishing faster.
Now I am runner also and I can tell you 42 years of running has taken its toll. I don't hurt or feel bad but the body does not respond I ran too much in my younger days. I would say your ride was great keep at it you finished a brutal ride.