Well done on the weight loss Shreck. I'm in about the same situation as you. I hope to do a club century in September. My fitness and ability to ride distances is continually rising but whether it will be good enough for a century (without undue suffering) is uncertain. I'm not too concerned about this - if not this year then next. There is a 75 mile option I can do that peels off from the longer ride. Also, the ability to ride longer distances without cramping is improving. As long as I'm seeing improvement I'm satisfied.

For riding in the heat, most of us have learned the tactic of freezing water bottles. For rides of 50 to 60 miles, I also slip fleece mittens over the two bottles on the bike and drink the bottle in the jersey pocket. The fleece keeps hot ambient air from flowing over the water bottle and from warming up before they are empty. It's a treat to have a very cold drink four or more hours into a ride.