Health Signs to Watch For following temp. fluctuations

Hi All! I just have a question concerning any health issues that might arise for my Crowntail, Finnegin. There was a recent power outage at my home and, therefore, his tank heater/filter were not working. The outage lasted approx. 36 hours and during that time, once his 10 gal. tank cooled off too much (IMHO) I transferred Finnegin to his original 2.5 gal. tank --filliing it with just 1 gal. and heated his bottled water on the stove (luckily we had gas, even tho' no electric). I gave him his favorite "resting" plant and cave, so he'd have something familiar and not freak out too much. I did water replacements with the warm water and eventually, when I just HAD to get some sleep, placed his bowl on a thick rug, pressed the side of his tank against the radiator, wrapped a thick towel around the remaining sides and put a cover on to try to keep the heat in. I est. his temp was 76 degrees (tho' turning up the thermostat had ME sweating bullets! LOL). He seemed to handle it well ..was swimming and ate his breakfast pellets. Also, yesterday, I placed his bowl on the center of the range and the heat from the pilot light helped keep him warm. Now that the power's back and he's back in his 82 deg. tank, I was wondering if there were any signs of "stress" or impending illness to look for. I know that temp. fluctuations are an enemy of a betta. Do you think he'll get ick? ...or something worse? I really tried as best as I could to "save his life" and just want to be sure I'm looking for the right clues if any illness is approaching. Thanks! All your advice/help in the past has been spot on!!